A former U.S. envoy to South Korea says North Korea has offered to return a U.S. spy ship that it seized in 1968 if top American officials visit Pyongyang.

Donald Gregg on Wednesday said the North made the proposal during his visit to Pyongyang last month, calling the idea a simple but necessary gesture.

A U.S. State Department official, however, ruled out a visit to the North by top officials in Washington.

Gregg, who has visited North Korea four times in the past ten years, has asked for the North to return the USS Pueblo on every trip.

The 906-ton ship was seized off the North's east coast in January 1968 during an intelligence mission.

One American sailor was killed during the seizure and 82 others were detained. They were released eleven months later after the United States apologized for spying.

The USS Pueblo is one of the primary tourist attractions in Pyongyang, North Korea.