A Japanese daily says North Korea asked the U.S. what reason it has to return to the six-way nuclear talks when U.S. special envoy Stephen Bosworth visited Pyongyang last week.

The Yomiuri Shimbun quoted a U.S. government official as saying Wednesday that Pyongyang made the inquiry when Bosworth urged the North to come back to the six-way talks and to reaffirm its obligations toward scrapping its nuclear program.

The paper said that North Korean officials told Bosworth that Pyongyang decided not to take part in the six-nation talks due to the U.N. Security Council’s adoption of a resolution in April that denounced the North for conducting a rocket launch.

The report said the North stressed the need for a reason to reverse its decision not to attend the nuclear negotiations.

The paper quoted another U.S. government official as saying that although it is unclear what exactly the North was seeking when it made the comment, an offer to ease U.S. sanctions could serve as reason enough for the North to return to the nuclear talks.

However, the report added that the U.S. did not make any offers during Bosworth’s North Korea visit.