Prime Minister Shinzo Abe moved closer to easing constitutional curbs that have kept Japan's military from fighting abroad since World War Two after the ruling party's dovish coalition partner agreed to consider a compromise proposal.
An agreement would be a big step toward achieving Abe's goal of loosening the limits of the post-war, pacifist constitution.
The New Komeito, the junior party in Abe's ruling bloc, is wary of a dropping a ban on sending Japan's military to aid a friendly nation under attack, but on Friday party officials agreed to consider a proposal that would allow the change while theoretically limiting cases in which it could be implemented.
"I want to discuss this thoroughly within the party," New Komeito deputy chief Kazuo Kitagawa told reporters after the latest round of talks, at which his ruling Liberal Democratic Party counterpart Masahiko Komura submitted the new proposal.
The United States and some Southeast Asian countries would welcome the change, which would mark a major shift in Japan's post-war security policy. Japan's military has never engaged in combat since its defeat in World War Two.
But rival China, locked in bitter disputes with Japan over territory and wartime history, would almost certainly criticise it as a sign that Tokyo, rather than Beijing, is ramping up regional tensions.