Acting defense secretary Patrick Shanahan speaks to reporters Tuesday after a classified briefing for members of Congress on Iran. (Patrick Semansky/AP)

The United States will deploy about 1,500 troops to the Middle East, President Trump said Friday, in his administration’s latest step to address what it says are increased threats from Iran.

“We’re going to be sending a relatively small number of troops, mostly protective, and some very talented people are going to the Middle East right now, and we’ll see what happens,” he said outside the White House. “It’ll be about 1,500 people.”

Acting defense secretary Patrick Shanahan said he had approved a request by U.S. Central Command, which oversees military activities in the Middle East, to deploy a Patriot missile battalion, intelligence and surveillance aircraft, a squadron of fighter planes, and engineering capabilities. Shanahan said the measures would help safeguard U.S. forces given an ongoing threat posed by Iran and its proxies.

“The additional deployment to the U.S. Central Command area of responsibility is a prudent defensive measure and intended to reduce the possibility of future hostilities,” Shanahan said in a statement. 

The decision was made after a meeting late Thursday at the White House between Trump and top Pentagon leaders. While the deployment represents a modest increase to the large U.S. military footprint in the Middle East, it marks the latest manifestation of a growing confrontation between Washington and Tehran that lawmakers worry could result in a miscalculation or open conflict.

The infusion of forces also came as the State Department notified Congress that Trump would be invoking emergency powers to sidestep the congressional approval process and sell arms to Saudi Arabia, the United Arab Emirates and other nations.   

Pentagon officials have been emphasizing that they are taking steps to deter Iran. In recent days, Shanahan has said that any new troop deployments would serve to ensure the protection of U.S. forces and avoid the risk of Iranian miscalculation that could lead to a broader conflict.

“Our job is deterrence. This is not about war,” he said Thursday. “We have a mission there in the Middle East: freedom of navigation, counterterrorism in Syria and Iraq, defeating al-Qaeda in Yemen, and the security of Israel and Jordan.”

The type of forces the Pentagon is deploying does not indicate any impending ground offensive by the United States. Patriot missiles are designed to track and shoot down incoming missiles.

Kathryn Wheelbarger, acting assistant defense secretary for international security affairs, said the additional forces would be going not to Iraq or Syria but to other U.S. positions in the Middle East that she declined to disclose.

“This is intended to be responsive to their aggressive behavior and planning and to defend our forces in the region,” Wheelbarger said. “We are seeking to avoid hostilities. We are not seeking war with Iran.”

The decision comes as the Trump administration is stepping up pressure on Iran after pulling out of the 2015 nuclear accord negotiated by President Barack Obama. Since then, the Trump administration has increased sanctions, designated Iran’s Islamic Revolutionary Guard Corps as a foreign terrorist organization and declined to renew waivers that allowed eight countries to buy Iranian oil.

In recent weeks, U.S. officials have cited new indications of possible Iranian attacks on U.S. interests as a reason to send the USS Abraham Lincoln Carrier Strike Group, four B-52 bombers and Patriot missile defense forces to the region. The State Department ordered the evacuation of all non-emergency personnel from Iraq, where Iranian proxy forces operate.

U.S. officials say they believe that Iran was behind sabotage attacks on four oil tankers off the coast of the UAE this month. Iran has denied involvement in the incidents, which damaged the ships. Two of the ships were Saudi Arabian, one was from the UAE and the fourth was Norwegian.

Rep. Mac Thornberry (R-Tex.), the top Republican on the House Armed Services Committee, defended the increased military posture announced Friday, saying it is “important that we make clear to Iran, in words and actions, that they cannot attack us with impunity.”

But Democrats have expressed skepticism about the urgency of the threats and voiced concern that the White House, under the guidance of national security adviser John Bolton, who has advocated for regime change in Iran, could rush into a conflict.

Rep. Adam Smith (D-Wash.), the Armed Services Committee’s chairman, called the new deployment “unsettling.”

“Without a clearly articulated strategy, adding more personnel and mission systems seems unwise, and appears to be a blatant and heavy-handed move to further escalate tensions with Iran,” he said in a statement.

The increased pressure by the United States has prompted a backlash by Iran, which announced this week that it has quadrupled the pace at which it enriches low-grade uranium at one nuclear plant. It predicted that within weeks it would exceed a stockpile cap set by the nuclear agreement.

A senior administration official on Friday accused Iran of using “nuclear blackmail” by threatening to stop meeting some of its commitments under the deal if European officials cannot figure out a way to get around U.S. sanctions by early June.

“We are trying to work as closely as we can with our allies to get them to hold fast on these fairly negative attempts at nuclear extortion and not give in to Iran’s demands,” said the official, who was not authorized to comment publicly and spoke to a small group of reporters on the condition of anonymity.

With Iran’s accelerated pace of uranium enrichment and the looming deadline for the Europeans to throw it a lifeline, the official said the Europeans must choose “whether or not they will give in to this kind of extortion or stand firm and make clear to Iran that there is one viable path for them, and that is to come to the table with us.”

Of the 1,500 additional troops being deployed to the region, some 600 of them are with a Patriot missile defense unit that is already there and will have its deployment extended, Vice Adm. Michael Gilday, director of the Joint Staff, said during a Pentagon briefing Friday.

Gilday said U.S. intelligence showed the attack on the oil tankers off the UAE was the result of limpet mines placed by the Islamic Revolutionary Guard Corps. He also said U.S. intelligence indicated that Iran was behind an attack this month on a Saudi oil pipeline.

“I can’t reveal the sources of that reporting except to say with very high confidence we tie the Iranians to those,” he said.

Gilday said the deployment of additional forces was designed to allow Central Command to get a better picture of the threat through surveillance and reconnaissance capabilities, harden defenses that the United States already has set up in the region, and respond to any attack if necessary.

He reiterated the Pentagon’s view that the actions the U.S. military has taken thus far — including the deployment of the USS Abraham Lincoln — appear to have deterred Iran from undertaking measures that were in preparation, particularly with regard to threats against U.S. forces.

“The secretary of defense recently said that he felt that the actions that we took changed the calculus of the Iranians. The attacks that we have seen thus far have not directly impacted U.S. forces,” Gilday said. “We think that through a combination of a very measured deployment of assets, as well as public messaging, we again are trying to underscore that we are not seeking hostilities with Iran.”

While incidents such as ship sabotage or drone attacks have been taking place for some time, Gilday argued that the difference this time was that the Pentagon views the latest incidents as a campaign by Iran over a specified period of time designed to disrupt various parts of the Middle East. He said the campaign was tying multiple threats together with a degree of complication.

Gilday added, “What their intent is, I think, is difficult to judge.”

Carol Morello, Anne Gearan and John Wagner contributed to this report.