China 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 claimed by the ruling Communist Party as part of its territory.

The companies are barred from importing goods into China or making new investments in the country, the Ministry of Commerce announced.

It wasn't clear what impact the penalties might have on Lockheed Martin or Raytheon. The United States bars most sales of weapons-related technology to China, but some military contractors also have civilian businesses in aerospace and other markets.

Taiwan and China split in 1949 after a civil war. The island never has been part of the People's Republic of China, but the Communist Party says it is obliged to unite with the mainland, by force if necessary.

President Xi Jinping's government has stepped up efforts to intimidate Taiwan by flying fighter jets and bombers near the island and firing missiles into the sea.