Prime Minister Takeo Miki conveyed concerns over U.S. President Gerald R. Ford’s planned visit to China in late 1975 during a meeting the month before, indicating worry that Washington was developing a closer relationship with Beijing, according to documents declassified Wednesday.

“We hope there will be no shocking consequences of the visit to China,” Miki told Ford during a meeting on the sidelines of a Group of Six — the first summit of what today is the Group of Eight leading countries — in Rambouillet, France, in November 1975, the documents show....