Japan’s Prime Minister Yukio Hatoyama has confirmed the existence of long-denied Cold War agreements that permitted U.S. nuclear-armed warships to visit Japanese ports in violation of Tokyo’s antinuclear principles.

According to Japanese media Wednesday, Hatoyama told reporters on Tuesday that despite the confirmation of the existence of the nuclear agreements previous conservative administrations had with the U.S., his government will hold fast to Japan’s three nonnuclear principles.

Japan declared in 1968 that it would not produce, possess or bring in nuclear arms. The three principles have since been regarded as national policy.

Hatoyama said he believes the recent revelations would not affect Japan’s relations with the U.S., adding that it is important to prevent the issue from affecting their bilateral relationship.