China on Thursday imposed trade and investment sanctions on U.S. military contractors Lockheed Martin and Raytheon for supplying weapons to Taiwan, stepping up efforts to isolate the island democracy, which the ruling Communist Party claims as part of its territory, The Associated Press reported.

Companies are banned from importing goods into China or making new investments in the country, the country's Commerce Ministry announced.

It is not yet clear what impact the fines may have on Lockheed Martin or Raytheon. The U.S. bans most sales of weapons-related technology to China, but some military contractors also have civilian businesses in aerospace and other markets.

Taiwan seceded from China in 1949 after the civil war.

Relations between Beijing and Washington are strained because of U.S. support for Taiwan independence.