BEIJING — China said on Friday that it would impose sanctions on American companies involved in the recently proposed sale of more than $2 billion in arms to Taiwan. The move could further strain ties between the two large powers, whose governments have been targeting each other’s businesses for punishment as a tariff war boils.

Beijing has threatened similar penalties after previous American weapons sales to Taiwan, a self-governing island that China considers a rogue part of its territory. The sanctions promised in those cases have not materialized so far.

But whether and how the Chinese government follows through this time could send a signal about officials’ willingness to inflict damage upon more American firms as the trade fight with Washington stretches into its second year.

“The United States’ arms sales to Taiwan constitute a serious violation of international law and the norms governing international relations,” Geng Shuang, a spokesman for China’s Foreign Ministry, said on Friday, without offering specifics on how and when the American companies involved would be penalized.