Japan and the United States yesterday ended one of their most difficult trade disputes by agreeing to open more than $8 billion in Japanese government procurement to international competition, including the $3.3-billion-a-year telecommunications equipment market.

The three-year agreement, signed in ceremonies in Washington and Tokyo yesterday, ends five years of discussions between the United States and Japan on government procurement policies and particularly on purchases by Japan's Nippon Telegraph and Telephone public corporation. It is part of the government procurement code fashioned during the Tokyo round of the multilateral trade negotiations.

"There have been more visable trade issues than NTT during the past year," U.S. Trade Represenative Rubin Askew said during signing ceremonies yesterday. "From a long-range perspective, however, none is more important to the United States than inclusion of NTT purchases under the requirements of the government procurement code."

The agreement doesn't automatically assure U.S. companies a share of Japan's government purchases, but it does give them a chance to compete in a relatively closed market.

"This is a dramatic change in Japanese telecommunications procurement policy and can be considered a victory for fair and open trade policy in the international marketplace," the Electronics Industries Association said.