Abe has repeatedly said he would not consider developing nuclear weapons, but the opposition alleged he was effectively suggesting the idea by proxy through his aides.

Abe, asked later by reporters if he felt he should dismiss the outspoken foreign minister, said: "I don't."

Abe said both he and Aso supported Japan's 1967 "three principles" of refusing the possession, production and presence of nuclear weapons on its soil.

"As I have told you all along, we are in agreement on the idea that we will firmly maintain the three non-nuclear principles. So I don't see any problem," Abe said.

Aso and Shoichi Nakagawa, a top policy aide to the premier, have both called for a frank debate on going nuclear in light of communist neighbor North Korea, which tested an atom bomb on October 9.

But both have stopped short of openly calling for the development of nuclear weapons.

The four opposition parties, in a joint statement delivered to Abe's office, said that dismissing Aso would "make clear your true intentions." The opposition told Abe to reply by Monday and threatened to disrupt parliament over the issue.

"The reply to the demand could affect parliamentary affairs," said Yukio Hatayama, the general secretary of the largest opposition Democratic Party of Japan.

Japan's opposition has been struggling to gain strength after years in the wilderness during the tenure of Abe's popular predecessor Junichiro Koizumi.

Abe, Japan's youngest prime minister since World War II, took office in late September pledging a conservative agenda after a race in which he defeated Aso.

Abe enjoys high popularity ratings, in part due to his unflinching criticism of North Korea.

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