A top defense policy adviser for Japan's government has proposed using U.S. President-elect Donald Trump's demand that Tokyo contribute more to its own defense as a chance to update the countries' security alliance to reflect Japan's greater military capability and today's harsher security environment.

Former Defense Minister Shiberu Ishiba, a leading candidate to become Japan's next prime minister, said Tokyo contributes more financially for the basing of American troops than any other U.S. ally, but perhaps less militarily.

Japan's pacifist constitution, written under U.S. direction after World War II, prohibits it from using force in settling international disputes. A security treaty requires the U.S. to help Japan if it is attacked and provides for U.S. bases in Japan.

Prime Minister Shinzo Abe has urged an expanded role for Japan's military.