The Lower House on Tuesday kicked off much-awaited deliberations on two contentious security bills that would greatly expand the scope of the Self-Defense Forces’ missions overseas, and opposition lawmakers immediately went on the attack.

One of the two bills would amend 10 security-related laws and thereby remove some restrictions on SDF operations. One of the revisions would allow Japan to exercise the right of collective self-defense, or the right to come to the aid of an ally under attack.

Opposition lawmakers argued that key passages in the bills are so vague it would allow the government to stretch the interpretation excessively to its own ends.

The Democratic Party of Japan, the largest opposition force, and the Japanese Communist Party oppose the bills, while Ishin no To (Japan Innovation Party), the second-largest opposition force, remain circumspect.

Their firmness on this has caused the ruling bloc to consider extending the Diet session from its currently scheduled June 24 end to sometime in early August to allow enough time for the bills to be enacted.

The ruling camp has a majority in both the Lower and Upper Houses and is capable of passing the bills regardless of opposition from other parties. But bulldozing them through the Diet would risk provoking a voter backlash in the Upper House election scheduled for summer 2016.

Polls have suggested a majority of voters still do not fully understand the bills and oppose their hasty enactment.

During Tuesday’s session, DPJ Secretary-General Yukio Edano argued that the wording of three conditions under which the government would use the right of collective self-defense is too vague.

“It’s tantamount to saying, ‘please leave it to the discretion of the government,’ ” Edano told the Lower House.

Under the bills, Japan would be allowed to use the right of collective self-defense only when three requirements are met: when there is clear danger to Japan’s survival, and when the threat could “fundamentally overturn” people’s right to life, liberty and pursuit of happiness; when there are no alternative means; and when the use of force can be limited to the minimum necessary level.

During the plenary session, Prime Minister Shinzo Abe said the deployment of the SDF overseas is “generally” banned under the war-renouncing Constitution. But minesweeping operations in the Persian Gulf could be one exception, he said.

Minesweeping “is a passive and limited action,” Abe said, stressing that such an operation would be very different from joining a combat coalition like those in the 1991 Gulf War or the 2003 Iraq War.

He said he believes a minesweeping operation in another nation’s territorial waters could certainly meet the three conditions for collective self-defense.

Abe’s discussion of “exceptions” has complicated the debate between government officials and opposition lawmakers.

Defense Minister Gen Nakatani, for example, has argued that as long as the three conditions are met, Japan can use the right of collective self-defense under the Constitution — and it is irrelevant whether the theater of action is another nation’s sovereign territory. This apparently contradicts Abe’s discussion of “exceptions.”

Abe has repeatedly referred to one scenario being a maritime minesweeping operation with no cease-fire in place in the Strait of Hormuz, because 80 percent of crude oil shipments to Japan pass through that narrow waterway.

Asked about the possibility of exposing SDF personnel to risks, Abe said that it is something they must bear in the course of their duties.

A joint poll by the Nikkei Shimbun and TV Tokyo conducted between Friday and Sunday found that 55 percent of 1,033 respondents were against the government’s plan to enact the bills by the end of the current Diet session. Only 25 percent supported Abe’s plan to pass the legislation in the current session.

Eighty percent of the respondents said the government has failed to explain what the bills will do. A mere 8 percent said they had heard enough.