NATO has begun to deploy Patriot missiles to Turkey to help Turkish troops repel attacks by missiles or aircraft from Syria.
The US European Command said its troops and equipment had started arriving in southern Turkey and more would arrive in the coming days.
Germany and the Netherlands are preparing to ship Patriot batteries early next week. The six battery units are scheduled to be operational by the end of January.
NATO approved the deployment of the surface-to-air missiles early last month, after a request from Turkey.
The United States, Germany and the Netherlands are each deploying two batteries of Patriot missiles, under the command of NATO along the Turkish-Syria border.
The BBC reports US personnel and equipment have begun arriving at the Incirlik Air Base in southern Turkey.
Patriot batteries from Holland will depart for Turkey on Monday and are expected to arrive there by 22 January along with nearly 300 troops, the De Telegraaf newspaper reports. Germany is following a similar schedule.