WASHINGTON (Reuters) - The United States added six companies to its trade restriction list on Tuesday, including four for their links to the training of China's military forces, according to a government posting.

Two of the companies are in China, one in South Africa, two in the United Arab Emirates and one in the United Kingdom.

Global Training Solutions Limited and Smartech Future Limited, both in China, as well as Grace Air (Pty) Ltd and Livingston Aerospace Limited of the United Kingdom, were added because of their ties to the Test Flying Academy of South Africa and the training of China's military forces using Western and North Atlantic Treaty Organization (NATO) sources, the posting said.

"This activity is contrary to the national security and foreign policy interests of the United States," it said.

UAE companies Mega Fast Cargo and Mega Technique Trading for evasive conduct, and Mega Fast Cargo's shipping U.S.-origin goods to Russia, it said.

The companies put on the trade restriction list, known as the Commerce Department's "Entity List," require licenses to ship U.S. goods and technology to them, which are likely to be denied.

(Reporting by Karen Freifeld; Editing by Doina Chiacu)