China said it would go ahead with threatened sanctions against U.S. companies selling arms to Taiwan unless they halted sales.

A Chinese Foreign Ministry spokesman, Ma Zhaoxu, told a news conference on Tuesday that U.S. arms sales to Taiwan severely hurt China's core interests.

On Friday, the Obama administration said it would sell a package of $6.4 billion of missiles, helicopters and other military hardware to Taiwan, the self-ruled island that Beijing deems an illegitimate breakaway.

China then said U.S. companies involved in selling the arms to Taiwan would face corresponding sanctions.

Companies that could be affected include Sikorsky Aircraft Corp, a unit of United Technologies Corp; Lockheed Martin Corp; Raytheon Co; and McDonnell Douglas, a unit of Boeing Co.

(Reporting by Chris Buckley and Ben Blanchard; Editing by Jonathan Hopfner)