President Trump’s last-minute decision to pull back from a retaliatory strike on Iran underscored the absence of appealing options available to him as Tehran races toward its next big challenge to the United States: building up and further enriching its stockpile of nuclear fuel.
Two weeks of flare-ups over the attacks on oil tankers and the downing of an American surveillance drone, administration officials said, have overshadowed a larger, more complex and fast-intensifying showdown over containing Iran’s nuclear program.
In meetings in the White House Situation Room in recent days, Secretary of State Mike Pompeo contended that the potential for Iran to move closer to being able to build a nuclear weapon was the primary threat from Tehran, one participant said, a position echoed by Mr. Trump on Twitter on Friday. Left unsaid was that Iran’s moves to bolster its nuclear fuel program stemmed in substantial part from the president’s decision last year to pull out of the 2015 international accord, while insisting that Tehran abide by the strict limits that agreement imposed on its nuclear activities. Mr. Trump has long asserted that the deal would eventually let Iran restart its nuclear program and did too little to curb its support for terrorism.
Now, with the immediate crisis over the drone abating, Mr. Trump has dispatched envoys to the Middle East to consult with allies as he and his national security team appear focused on a two-tier strategy for confronting the nuclear issue. First, they intend to maintain and intensify the sanctions the United States has used to squeeze Iran’s economy, chiefly by choking off its ability to sell oil to the world.
During White House deliberations, Mr. Pompeo and others made the case that Tehran’s lashing out in the Persian Gulf was in direct response to the sanctions. He and Mr. Trump are telling allies and members of Congress that Iran’s leaders will eventually no longer be able to tolerate the devastating economic and domestic political costs, perhaps forcing them to agree to a new nuclear accord tougher than the one they negotiated with President Barack Obama.
At the same time, administration officials have signaled that they continue to weigh more aggressive options, including military strikes and cyberattacks. Those options could come into play if Iran does not buckle under economic pressure or follows through on the warning it issued on Monday: that it would breach the 2015 accord’s limits on how much low-enriched nuclear fuel it can hold, and that it was pointedly leaving open the possibility of further enriching the fuel, edging it closer to the purity necessary to build a bomb.
Mr. Trump’s hawkish national security adviser, John R. Bolton, arrived in Israel on Saturday for a previously scheduled meeting with his Israeli and Russian counterparts to discuss what the White House calls “regional security.”
While there he will meet with the head of the Israeli Atomic Energy Commission and other officials who, during the Obama administration, repeatedly ordered practice bombings to simulate taking out Iran’s nuclear facilities. Israel stopped short of bombing but, a decade ago, joined the United States in conducting a sophisticated cyberattack against Iran’s major enrichment site.
As Iran vows to gradually kick its nuclear production back into gear, both options are being revisited, officials say, in case Iran carries through its declared nuclear plans. This coming week it is likely to have amassed more than 660 pounds of low-enriched uranium, the limit set in the 2015 pact.
The marginal move over the limits “might not be a big deal,’’ said Philip H. Gordon, a former State Department official now at the Council on Foreign Relations, “but exiting the nuclear deal is a big deal because it’s a slippery slope toward not having any of those constraints at all.”
But stopping those activities, with a military attack or the kind of complicated online sabotage that the United States and Israel conducted a decade ago, would carry huge risks. And this time, the element of surprise would be gone.
The State Department’s Iran coordinator, Brian Hook, is also in the gulf, trying to coordinate a response — and perhaps an opening for talks with Tehran — with Saudi Arabia, the United Arab Emirates, Kuwait and Bahrain, all among Iran’s greatest rivals. The State Department did not say whether he would go to Oman, which acted as the back channel for opening nuclear negotiations during the Obama administration.
Missing from any coalition, at least for now, are the Europeans, the Chinese and the Russians, all of whom participated in those negotiations and say that Mr. Trump created the current crisis by abandoning a nuclear accord that was working, even if imperfectly.
“Trump thinks that if he just turns the oil spigot off the Iranians, and bring crude oil revenue to near zero, the Iranians will fold negotiate a new deal,” one European official who was deeply involved in negotiating the agreement said, speaking on the condition of anonymity to avoid alienating the administration. “It won’t work.”
Some leading members of Congress and current and former diplomats say the bet that sanctions will drive the Iranians to the negotiating table — and force them into a more restrictive deal than they gave Mr. Obama — is a fantasy.
“The question is how do the Iranians react now,” said Senator Jack Reed of Rhode Island, the top Democrat on the Armed Services Committee. “Will they give up or act much more aggressively to get out of this dilemma? What we are seeing is that they act more aggressively.”
Iran, he said, is practiced at both tolerating international isolation and carrying out asymmetric warfare — finding targets it can hit despite having far less traditional military ability than the United States — and can be expected to ramp up counterpressure before the loss of oil revenue completely cripples it.
Two weeks ago Iran’s supreme leader, Ayatollah Ali Khamenei, rejected any negotiation with the United States.
“Khamenei has made it clear in his speeches: He sees an American plot to weaken Iran and lure it into negotiations,” said Suzanne Maloney, an Iran expert at the Brookings Institution. “And so after a long waiting period, they are choosing this moment to escalate, so far in a carefully calibrated way. But they have many more options.”
In fact, while Iran is weaker economically than it was a year ago, it has developed skills it did not possess during the last major nuclear crisis. It can strike ships with more precision and shoot planes out of the air. It now has a major cyber corps, which over the last seven years has paralyzed American banks, infiltrated a dam in the New York suburbs and attacked a Las Vegas casino.
These abilities have altered the risk calculations, making the problem Mr. Trump faces with Iran even more vexing than those that confronted President George W. Bush or Mr. Obama.
The least-fraught course for the United States is to bank on sanctions eventually working. Under tighter sanctions, Iran’s economy has contracted sharply and inflation is running at 50 percent.
But sanctions themselves are not a solution; they are a means to getting a country to change its behavior. Sometimes nations resist: Decades of sanctions against Cuba failed to have the intended effect. In Iran’s case, its old logic — that it could wait out the Trump administration — has been replaced by a new theory, that the United States will relent only when it begins to suffer as well.
The Europeans and Russians have talked about setting up a barter system to avoid American-imposed sanctions and keep Iran complying with the deal, but so far those efforts have come to naught.
The test may be how far the Iranians go in breaking free of the current nuclear limits. If they hover just above the ceilings set in the 2015 pact, but do not race to return to where they were a few years ago, their defiance may not blossom into a crisis. If the Iranians aggressively increase the size and potency of their fuel stockpile, Mr. Reed said, the administration might “make a case the nuclear threat has grown enough that we have to act.”
If he cannot make progress by relying on sanctions, Mr. Trump will almost certainly find himself being pressured, perhaps by Saudi Arabia or Israel, to “solve” the nuclear problem by taking out Iran’s facilities.
In the first year of the Trump administration, Lt. General H.R. McMaster, the president’s second national security adviser, ordered that the plans to do so be updated. But the Iranians have not been sitting still, either.
To reduce its vulnerability to airstrikes, Iran has built mazes of underground bunkers, tunnels and compounds to house many of its nuclear facilities — especially those involved in making nuclear fuel, the main hurdle to building an atom bomb.
At Natanz, the primary uranium enrichment site, the desert around the facility has been ringed with antiaircraft guns. In 2007, satellite images showed Iran building a tunnel complex nearby, suggesting new precautions to shield from aerial strikes.
Similarly, Iran has sought to harden its sprawling nuclear complex at Isfahan, where uranium ore is turned into a gas that can be spun to produce enriched uranium.
If they are attacked, the Iranians appear to have the capacity to respond, including militias and proxies near the gates of American bases in Iraq, Afghanistan and elsewhere in the Middle East.
A decade ago, facing the same dilemma about Natanz that Mr. Trump faces now, the Obama administration, along with Israel, stepped up a covert operation, known as Olympic Games. The attack on Iran’s centrifuges used computer code that sped up and slowed down their nuclear centrifuges until they spun out of control.
The Iranians did not see it coming. They spent more than a year trying to determine why their centrifuges were exploding, and spreading radioactive material inside the plant’s giant underground enrichment hall. They learned the answer when the code was accidentally released.
While the National Security Agency and United States Cyber Command have looked at other cyberoptions — including Nitro Zeus, a plan to shut down the country’s power grid and communications systems in the opening days of a war — they concluded the effects on Iran’s population could be huge. Narrower, stealthy attacks would be difficult, because the Iranians are now looking for a second wave.
More worrisome, the Iranians have built their own online corps, and have been increasingly effective breaching American banks and power systems, and have even experimented, in small ways, with influence operations during the midterm elections, the government reported.
Mr. Trump’s other option would be to reverse course, as he did with North Korea, and move from threats to a diplomatic embrace. He has regularly telegraphed his desire to open a channel for negotiation, and many countries and politicians have volunteered to act as intermediaries, most recently Prime Minister Abe of Japan, whose entreaties were rejected by Iran’s supreme leader.
But Iran is not like North Korea. There is not one power center, no figure like Kim Jong-un to meet. The military and the clerics have a role. The 2015 agreement was negotiated between Secretary of State John Kerry and Iran’s foreign minister, Mohammad Javad Zarif, over a period of years; President Obama never met President Hassan Rouhani.
Moreover, the Iranians have said that Mr. Trump must first re-enter the old deal before negotiating a new one. Mr. Trump has refused, and Mr. Pompeo has said that to come to an accord, the Iranians must comply with his demands for 12 huge changes in their behavior, like ceasing support of terrorism and giving up all things nuclear.
“I can imagine talks,” Mr. Gordon said. “What’s harder to imagine is the deal would come anywhere close to what the Trump administration says is an absolute minimum.”