Aso has been at the forefront of pushing for Japan -- the only country to have been attacked with atomic bombs -- to debate the nuclear option.

Prime Minister Shinzo Abe has ruled out even discussing building nuclear weapons, but the issue has caused concern in neighboring countries.

Experts have long believed Japan has the knowhow to develop nuclear weapons quickly, in part because it relies on nuclear technology for nearly a third of its energy needs.

"Technologically speaking, we have the capability to develop atom bombs and we have the ability to launch satellites with rockets. We also have plutonium, under the supervision of the IAEA," or International Atomic Energy Agency, Aso said.

Aso met later in the day with IAEA chief Mohamed ElBaradei, who is visiting Japan in part for talks on North Korea's nuclear program.

Aso was responding to a question by the opposition, which has called on Abe to sack the foreign minister to show his commitment against nuclear weapons.

Aso reiterated the government's view that Japan has the right to nuclear weapons despite its pacifist constitution, which was imposed by the United States after World War II.

"From a purely theoretical viewpoint, possession of a necessary minimum of nuclear weapons for the purpose of self-defense is not banned under the current constitution," Aso said.

Japan is particularly concerned about North Korea, which launched a missile over Japan's main island in 1998. The communist regime tested its first atomic bomb on October 9.

Under a 1967 policy, Japan refuses the production, possession or presence of nuclear weapons on its soil.

US nuclear bombs obliterated the Japanese cities of Hiroshima and Nagasaki in the closing days of World War II, killing more than 210,000 people.

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