WASHINGTON (Reuters) - The United States is pursuing the sale of more than $2 billion (1.6 billion pounds) worth of tanks and weapons to Taiwan, four people familiar with the negotiations said, sparking anger from Beijing which is already involved in an escalating trade war with Washington.

An informal notification of the proposed sale has been sent to the U.S. Congress, the four sources said on condition of anonymity because they were not authorized to speak about the possible deal.