Japan's Prime Minister Takeo Fukuda said yesterday he has assurances from President Carter that U.S. ground forces will be withdrawn from South Korea gradually and 'in a way not upsetting the peace on that peninsula."

In an interview on "issues and Answers" (ABC, WMAL), the Japanese leader indicated Carter intends to strengthen U.S. air power in South Korea and to take other compensating measures.

"Roughly, I think that is what he has in mind," Fukuda said.

Fukuda said his own country could not increase its own military strength except for some "qualitative aspects."

"If we spend too much money on defense that will cause apprehension for Asian people," he said.

On another subject, Fukuda, who had talks last week with Carter, affirmed Japan's intention to develop nuclear power plants for civilian purposes-despite the President's disapproval.

"This matter is just about the only issue that still remains between our two countries," Fukuda said.

The prime minister said he was even more dedicated than Carter to the elimination of nuclear weapons. However, he said, "nuclear energy is very necessary for the peaceful devel opment of countries like Japan. There should not be anything to stand in the way of peaceful development."

Carter's concern is that the plutonium produced in such plants is useful in making nuclear weapons. Fukuda said the issue is not insoluble. "I do hope we can have amicable and smooth discussion about this," he said.

On human rights, the Japanese leader said he agreed with Carter's objectives but there are "different approaches."

"In some cases it may be well to speak out loud but in others it may produce a failure instead of a success in the end. And then, with all the noble cause, you are not achieving what you are after," Fukuda said.

The 40,000 U.S. ground forces in South Korea are considered both a barrier to attack from the Communist north and a shield for Japan and other democratic countries in Asia. Fukuda said he told Carter "very frankly that the Asians are very importantly concerned" about his plans for a withdrawal.