U.S. officials say the United States’ military presence in Jordan has expanded to around 1,000 troops.
The deployment is described as a show of force aimed at preventing the war in neighboring Syria from spilling over into U.S. ally Jordan.
The U.S. deployment includes F-16 fighter jets and Patriot air-defense missiles.
A U.S. official said around 700 troops that had deployed to Jordan for a major joint exercise, which ended this week, will remain in the kingdom at the request of the Jordanian government. Some 250 U.S. troops were earlier deployed in Jordan.
The Obama administration last week said it was ready to start arming Syrian rebels.
The announcement came as Washington said it had proof the Syrian government had used chemical weapons.
In another development, Russian President Vladimir Putin said Moscow believes some 600 Russians and Europeans are fighting on the side of the Syrian rebels.
Speaking on June 21 in St. Petersburg, Putin also warned Western countries against arming the Syrian opposition, saying it remained unclear which forces are aligned with the rebels.
Russia is a leading ally and arms supplier to the Syrian government and opposes outside involvement in the conflict.
Based on reporting by AP, AFP, Reuters, ITAR-TASS, and Interfax