The United States has sent a significant amount of naval power to the Middle East in recent weeks, including two aircraft carriers, their support ships and about 2,000 Marines.
Washington is on heightened alert for activity by armed groups as regional tensions soar during the Israel-Hamas war.
“Following detailed discussions with President (Joe) Biden on recent escalations by Iran and its proxy forces across the Middle East Region, today I directed a series of additional steps to further strengthen the Department of Defense posture in the region,” Defense Secretary Lloyd Austin said in a statement.
Austin stated he was placing additional troops on prepare-to-deploy orders, but did not say how many.
The Pentagon has already placed some 2,000 troops on a heightened state of readiness in case they need to deploy to the region.
“These steps will bolster regional deterrence efforts, increase force protection for U.S. forces in the region, and assist in the defense of Israel,” Austin added.
The deployments come two years after Biden’s administration withdrew air defense systems from the Middle East, citing a reduction in tensions with Iran.
The Patriot, considered one of the most advanced US air defense systems, is usually in short supply, with allies around the world vying for it.
The THAAD system has a powerful radar. US deployment of the system to South Korea in 2016 angered China, which believed it could peer into its airspace.
There has been a spike in attacks against US forces in Iraq and Syria since the conflict between Israel and Hamas fighters in Gaza broke out.