A White House announcement that the United States will deploy an aircraft carrier and Air Force bombers to counter Iranian threats came into sharp focus Monday as U.S. officials said the message followed a specific threat and a request from the top U.S. general overseeing Middle East operations.

Acting defense secretary Patrick Shanahan said in tweets Monday that he approved the request Sunday, describing it as a “prudent repositioning of assets in response to indications of a credible threat by Iranian regime forces.”

“We call on the Iranian regime to cease all provocation,” Shanahan wrote. “We will hold the Iranian regime accountable for any attack on U.S. forces or our interests.”

The proposal to send the USS Abraham Lincoln and its associated escort ships and Air Force bombers to the region originated with U.S. Central Command, which oversees operations in the region, a defense official said. The official was not authorized to speak publicly and requested anonymity.

Marine Gen. Kenneth McKenzie, who recently took over leadership of Centcom, has visited the Middle East several times recently. McKenzie submitted the request Sunday, and it was approved by Shanahan, the official said.

“We’ve been tracking a variety of threat streams for some time,” the official said, but Centcom detected “specific and credible” information that differed from those previous threats in recent days. The threats involved Iranian military forces and proxy forces, and indicated potential actions against U.S. military personnel and nonmilitary interests on land and at sea.

A Pentagon spokesman, Charles E. Summers Jr., said in a statement that the Defense Department “remains integrated with the rest of the government’s efforts to address malign Iranian behavior.”

The new information appeared to show a shift within Iran’s response to steps by the Trump administration, including sanctions, measures to limit Iranian oil sales and the designation of Iran’s Revolutionary Guard Corps as a foreign terrorist organization.

It also threatens to delay the Pentagon’s ongoing efforts to reorient itself for “great power competition” against China and Russia, with U.S. officials describing China as its No. 1 concern in coming years.

The announcement came with the Lincoln more than 1,000 miles away from the Persian Gulf, timing that puzzled some defense analysts.

John Bolton, President Trump’s national security adviser, said in a statement Sunday night that “in response to a number of troubling and escalatory indications and warnings,” the United States would send the USS Abraham Lincoln Carrier Strike Group and a bomber task force to “send a clear and unmistakable message to the Iranian regime that any attack on United States interests or those of our allies will be met with unrelenting force.”

“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 Guard Corps, or regular Iranian forces,” Bolton’s statement said.

But the aircraft carrier won’t be there immediately.

Photographs routinely released by the Navy show it was off the coast of Greece and Italy on Friday in the Ionian Sea. For the Lincoln to steam off the coast of Iran, it must travel through the Mediterranean Sea, the Suez Canal, the Red Sea and the Gulf of Aden.

Administration officials initially offered little explanation Monday for the decision, which comes two years after Trump and U.S. military officials said they were sending another aircraft carrier, the USS Carl Vinson, to deter North Korea at a time when Trump had threatened Pyongyang. The Vinson and its associated escort ships eventually traveled north from Singapore, but only after spending days steaming in another direction.

But by Monday afternoon, defense officials began describing new, specific concerns that prompted the decision.

The Navy announced the deployment of the Lincoln on April 8, a week after it departed from Norfolk. Croatian news reports suggested that the Lincoln would soon head into its port of Split, but a U.S. defense official said Monday that the carrier will now “expedite its arrival” in the Middle East “in order to defend American forces and interests in the region.” U.S. military officials did not say Monday whether the port visit will be canceled.

The Navy’s top officer, Adm. John Richardson, downplayed the unusual nature of the White House announcing the deployment, saying the news was a “great demonstration” of a Pentagon concept known as “dynamic force employment,” in which forces are supposed to be more agile and less predictable.

“It is particularly germane to naval forces, which are dynamic by their nature,” Richardson said, speaking Monday at a naval conference outside Washington. “These are maneuver forces by design. They are designed to move around the globe fluidly in response to changes in security situations.”

Richardson said he found it “very encouraging” that the Lincoln can move if requested by “national leadership,” though naval forces have done so for decades. He declined to say whether the security environment with Iran has changed, referring a reporter’s question back to Bolton’s comments.

Becca Wasser, who studies the Middle East for the Rand Corp., said Bolton’s statement appeared to “leverage” an already planned deployment to the Middle East to send a message to Iran.

“While the U.S. has varied its carrier presence in the Middle East to be operationally unpredictable, these deployments are often planned well in advance and are not sudden decisions,” she said. “It’s important to note that the Lincoln strike group was already on a scheduled deployment, not that it was abruptly ordered to deploy by the White House.”

Micah Zenko, a political scientist with the McChrystal Group, called Bolton’s statement “alarmist” and noted that it fell outside the norms of how the Pentagon describes such deployments.

The sharp rhetoric from Washington comes after a relatively quiet period at sea between the U.S. and Iranian navies. Between January 2016 and August 2017, the Pentagon recorded dozens of interactions with Iranian vessels at sea that it considered unsafe and unprofessional, only for them to dry up.

The shift, first reported by the Wall Street Journal in January 2018, has held up since then, a U.S. military official said, speaking on condition of anonymity due to the sensitivity of the issue.

Bolton’s statement also cited the future deployment of Air Force bombers, which have been in and out of the Middle East for years and were deeply involved in the U.S.-led military campaign against the Islamic State. A U.S. defense official said the Defense Department is now working with the Air Force to determine which planes and people will deploy.

Lawrence Brennan, a retired Navy captain and adjunct professor at Fordham University, said that while the deployment of the Lincoln “should be routine,” the announcement of a threat against U.S. forces “is the big difference.”

“I don’t know the source of that intelligence or the true nature of that perceived threat,” he said.

The Trump administration announced last month that it was naming Iran’s Revolutionary Guard Corps as a foreign terrorist organization as it sought to find new ways to put pressure on Tehran.

The Pentagon and U.S. intelligence agencies have long said the Revolutionary Guard is responsible for activities that threaten U.S. troops and other Westerners, but previously administrations were reluctant to designate the group as a foreign terrorist organization, in part because of concerns that other nations could use the designation as a precedent against U.S. actions abroad.