WASHINGTON — The White House announced on Sunday that the United States was sending an aircraft carrier strike group and Air Force bombers to the Middle East because of “troubling and escalatory indications and warnings” related to Iran.
The deployment was intended “to send a clear and unmistakable message to the Iranian regime that any attack on United States interests or on those of our allies will be met with unrelenting force,” said John R. Bolton, the national security adviser, in a statement released Sunday night.
The announcement did not give any further information on the reasons for the commitment of military forces. An American military official said on Sunday night that whatever threat Mr. Bolton cited had most likely emerged in the previous 24 to 48 hours because as of late Friday, military analysts were not tracking any new, imminent or clearly defined Iranian or Iranian-backed threats against Americans in Iraq or the region.
Secretary of State Mike Pompeo, when asked by reporters about Mr. Bolton’s statement on a flight to Finland, said, “It’s something we’ve been working on for a little while.”
“It is absolutely the case that we have seen escalatory actions from the Iranians, and it is equally the case that we will hold the Iranians accountable for attacks on American interests,” he said. “If these actions take place, if they do by some third-party proxy, a militia group, Hezbollah, we will hold the Iranian leadership directly accountable for that.”
There have been escalating rounds of fatal violence between Hamas, the armed Palestinian group in Gaza, and the Israeli military in recent days, but an American official said that was not related to the military ramp-up in the Persian Gulf. Although Iran has provided financing to Hamas, there is no sign that it was involved in the recent rocket attacks against Israel.
“The United States is not seeking war with the Iranian regime, but we are fully prepared to respond to any attack, whether by proxy, the Islamic Revolutionary Guards Corps or regular Iranian forces,” Mr. Bolton said in the statement.
The carrier group heading to the Persian Gulf is that of the U.S.S. Abraham Lincoln, which has been in the Mediterranean Sea. There is no carrier strike group currently in the Persian Gulf, but such groups often transit through those waters since the Suez Canal is in the region.
At the end of April, the Abraham Lincoln and its fleet of accompanying ships trained alongside other American vessels and military units from the United Kingdom, Spain and France.
A Pentagon spokesman confirmed the military moves as outlined in Mr. Bolton’s statement but declined to provide more details.
The Trump administration has taken a hard-line policy against Iran and has said it aims to force Iran to lessen or end its support for Shiite militias and other groups across the Middle East.
One year ago, President Trump withdrew from a nuclear deal that world powers had reached with Iran in 2015, and he has since imposed harsh sanctions intended to force political change in Tehran. Mr. Bolton and Mr. Pompeo have been the leaders in formulating the new hard-line policies, often in direct opposition to recommendations from the Defense Department and C.I.A.
Last month, the Trump administration designated the Revolutionary Guards as a terrorist organization. The move imposes economic penalties and travel restrictions on members of the group, a unit of Iran’s military, and anyone else who deals with it. The terrorist designation was the first time the United States had made that move against a part of another nation’s government.
Although Mr. Bolton and Mr. Pompeo pushed hard for the designation, defense and intelligence officials opposed it out of concern Iran would take reciprocal action against American military personnel and intelligence operatives or launch attacks.
On Tuesday, President Hassan Rouhani of Iran signed a bill into law that declared all American troops in the Middle East terrorists and labeled the United States government a state sponsor of terrorism.
On Thursday, the Trump administration allowed oil purchase waivers for Iran to expire, in an effort to cut off all revenue that Iran gets from export of its oil. Last November, when it imposed major sanctions on Iran, the United States gave six-month waivers to eight nations to continue buying oil. American officials had signaled to the countries this spring they would continue the waivers, but made a surprise announcement last month that the waivers would end. China and Turkey, two of the customers, have said they oppose the American sanctions.
On Friday, American officials announced they would extend most waivers that allow some countries to work with Iran on a limited civil nuclear program, but said the waivers would be good only for 90 days.
Last month, Republican and Democratic senators asked Mr. Pompeo whether the administration would explicitly seek congressional approval before trying to enter a war with Iran. Mr. Pompeo demurred, saying lawyers should answer that question.
Senator Rand Paul, Republican of Kentucky, insisted that the United States could not attack Iran as part of a war authorization allowing the use of military force against Al Qaeda and other extremist groups deemed responsible for the attacks of Sept. 11, 2001.
Mr. Pompeo has said Iran bears more responsibility for ongoing violence in the Middle East than any other actor, even though the American military has been focused on fighting the Islamic State, a Sunni extremist group to which the Shiite government of Iran is opposed. The Iranian military has helped the Shiite-led government of Iraq combat the Islamic State, which had seized territory in northern Iraq and eastern Syria.
Iranian forces and their proxy fighters have generally refrained from attacking American troops in recent years.
At the height of the Iraq war in the mid-2000s, Iranian military officials helped train Iraqi Shiite militias to fight American troops and aided in the building of powerful explosive devices used against American armored vehicles. The Pentagon has said at least 603 American personnel were killed in Iraq by Iran-backed fighters — 17 percent of all Americans killed in hostile action there.
Last month, a bomber task force composed of six Air Force B-52 bombers and 450 troops from Barksdale Air Force Base in Louisiana returned to the United States after training in Britain. It is unclear if the same unit is redeploying to the Middle East.