United States Defence Secretary Leon Panetta has signed an order for the immediate deployment of two batteries of Patriot missiles and 400 troops to Turkey.
Germany and the Netherlands are also each sending two batteries of surface-to-air missiles to southern Turkey.
The BBC reports all six will be placed under the command of NATO and are scheduled to be operational by the end of January.
Turkey says it needs the defence batteries to shoot down any missiles that might be fired across the border from Syria.
The Bundestag in Germany on Friday approved the deployment by 461 - 86 votes.
Each battery consists of a command post, a radar to track incoming missiles and up to eight launchers with up to eight Patriot missiles each.
The system can simultaneously track 50 targets and shoot down five. It takes about 85 soldiers to work one battery plus logistical support.
Patriot missiles have a maximum range of 20 km.
