Japan and the United States are considering allowing U.S. Navy warships to undergo extensive repairs at private shipyards, enabling the ships to stay longer in Japanese waters without returning home for maintenance, government sources said Friday. The issue is expected to be discussed when Japanese Prime Minister Fumio Kishida travels to the United States to meet President Joe Biden in April, according to the sources. Such a deal is expected to improve the efficiency of U.S. military operations based in Japan amid China’s growing military assertiveness in the region. So far, Japanese private c…