U.S. pressure influenced Japan's decision in the 1970s to set narrow territorial sea limits in five of its key straits to enable safe passage of U.S. warships carrying nuclear weapons, declassified documents from the U.S. National Archives showed Sunday.

The declassified U.S. documents suggest the U.S. government, under pressure from the military, asked Tokyo not to extend its territorial waters in the five lanes — including the Soya and Tsugaru straits — to avoid hindering Washington's strategy for nuclear war.

The documents were found at the U.S. National Archives and Records Administration by Shoji Niihara, an expert on the history of Japanese-U.S. relations.