By Linda Sieg and Nobuhiro Kubo
TOKYO, April 3 (Reuters) - Japanese Prime Minister Shinzo Abe's government and ruling party are close to a consensus on the need to ease the pacifist constitution's constraints on the military's ability to fight alongside allies abroad, but have yet to persuade their junior coalition partner to agree to the historic change.
Allowing Japan's Self-Defense Forces to aid the United States or other friendly nations under attack would mark a major turning point for Japan's post-war pacifism and its military, which has not fired a shot in conflict since World War Two.
But Abe's effort to lift the ban on so-called collective self-defence faces opposition from his dovish coalition partner, the New Komeito. The move would increase the chance of involvement in wars overseas and almost certainly further strain ties with China and South Korea, already frayed by territorial rows and disputes over Japan's wartime past.
"There are various opinions inside the Liberal Democratic Party (LDP), but the view that it is possible to exercise the right of collective self-defence in a limited way is coming to be shared," Tadamori Oshima, an influential lawmaker in Abe's party, told Reuters in an interview.
"What is important politically going forward is whether we can get the understanding of New Komeito," Oshima added. "There is a great allergy in the New Komeito to the very idea of allowing the exercise of the right of collective self-defence."
Abe aims to achieve the change - part of his conservative agenda to make Japan a "normal country" more able to defend itself and its allies - through a cabinet decision rather than a politically tougher amendment to the constitution.
This week, his government unveiled a major overhaul of a decades-old ban on weapons exports. Longer term, Abe wants to formally revise the U.S.-drafted constitution, seen by conservatives as overly restricting Japan's security options.
Past governments have said Japan had the right of collective self-defence under international law but that the constitution's war-renouncing Article 9 prohibited it from taking such action.
Abe and his advisors argue Japan's challenging security environment, including China's military buildup, requires a more flexible approach and a bigger role for Tokyo in its alliance with Washington - something the United States has long urged.
Expressions of concern from within the LDP - as much over what party critics saw as Abe's high-handed decision-making style as over policy content - and from New Komeito, however, have delayed a decision on the contentious change.
Abe had faced push-back from LDP members, some of whom were upset by his seeming haste to make a decision without more careful discussion inside the party. One outspoken party critic said a change of such magnitude should only be achieved through a constitutional amendment.
Some political experts also suggested the debate smacked of a political performance intended to persuade the public.
Opinion polls show a majority of voters oppose lifting the ban, apparently reflecting wariness of getting dragged into foreign wars and support for the constitution's pacifist ideals.
OPENING THE DOOR
Faced with such obstacles, the government is stressing that any change will be limited and won't entail sending Japan's military to fight wars in far-flung lands.
"We will not suddenly take on the entire concept of collective self-defence. For example, we would not go to help America fight in Africa," an Abe administration source told Reuters.
"On the other hand, the ban on exercising the right of collective self-defence means there are various things we cannot do under current law that are necessary to protect Japan."
Among the examples cited are defending a U.S. vessel that comes under attack on the high seas when a Japanese navy ship is near by, shooting down a North Korean ballistic missile headed for the United States, and taking part in joint mine-sweeping operations during a conflict that blocks a vital sea lane.
"To go to war together (with an ally) would touch on the constitution," said the administration source, who declined to be identified because delicate talks were ongoing. "We have no intention of changing the interpretation to that extent."
Critics, including some constitutional scholars, however, say any such reinterpretation would make a mockery of formal amendment procedures and essentially gut Article 9, opening the door to bigger changes later despite assurances to the contrary.
Article 9 renounces Japan's right to go to war and to use force or the threat of force to settle international disputes. It also prohibits the maintenance of armed forces, although that ban has long been stretched to allow the country to have a military, now on a par with that of France.
"Abe knows that once even a tiny hole is opened, he and future conservatives can make the hole bigger with less popular resistance," said Sophia University professor Koichi Nakano, a member of a group of academics opposed to the change.
Whether and to what extent the New Komeito, which is backed by a Buddhist lay organisation, will agree to such changes is as yet unclear, although the party has a track record of compromising during its 15-year partnership with the LDP.
New Komeito leader Natsuo Yamaguchi has repeatedly expressed wariness about changing the long-standing government interpretation, but some in his party agree that growing security threats require a more flexible response.
"We can't yet see how it will all work out," a New Komeito source, who declined to be identified because he was not authorised to speak on behalf of the party, told Reuters.
"The majority view in the party so far is that we should continue to ban the exercise of the right of collective self-defence. But then ... some wonder is that really all right? Won't there be cases where it is necessary?"
Some New Komeito members say Japan can widen the scope of possible military action under the rubric of individual self-defence, leaving the ban on collective action formally in tact. But that would be unlikely to satisfy Abe, who has long favoured lifting the ban as a symbolic as well as practical move. (Editing by Dean Yates)