The United States is deploying a military contingent to a base in Saudi Arabia that has been abandoned for the past 15 years, officials say, marking a major escalation in tension with Saudi's regional arch-nemesis Iran. 

The forces deploying to Prince Sultan Air Base, 85 miles south of Riyadh, include fighter jets, air defense missiles and likely more than 500 troops, U.S. officials said on Friday.

Senior American defense officials said some U.S. troops and Patriot air defense missile systems have already arrived at the base, which was abandoned by Washington after it toppled Iraqi strongman Saddam Hussein in 2003.

'In coordination with and at the invitation of the Kingdom of Saudi Arabia, the Secretary of Defense has authorized the movement of U.S. personnel and resources to deploy to Saudi Arabia,' U.S. Central Command said in a statement. 

'This movement of forces provides an additional deterrent, and ensures our ability to defend our forces and interests in the region from emergent, credible threats,' Central Command said.