Glyn Davies, the U.S. special representative on North Korea, also said he wasn't aware of Mr. Iijima's trip.

WSJ: Trip to Pyongyang Irks Tokyo's Allies

Few details of Mr. Iijima's visit to Pyongyang have been made available.

WSJ: Trip to Pyongyang Irks Tokyo's Allies

He questioned whether Seoul's reaction to Mr. Iijima's visit was productive.

WSJ: Japan to Follow Own Path on Abductees

Mr. Iijima said upon landing in Beijing from Pyongyang on his way back to Tokyo Friday evening that he wouldn't be releasing any details of his visit.

WSJ: Trip to Pyongyang Irks Tokyo's Allies

Few details of Mr. Iijima's visit have been revealed.

WSJ: Japan to Follow Own Path on Abductees

The U.S. and South Korea last week warned that the trip to Pyongyang by Mr. Iijima, a top adviser to the Abe cabinet, may hurt efforts to pressure North Korean leader Kim Jong Un.

WSJ: Japan to Follow Own Path on Abductees

Mr. Iijima was a top adviser to former Prime Minister Junichiro Koizumi, and was deeply involved in organizing his visit to North Korea for talks with then-leader Kim Jong Il in the early 2000s, which led to the release of several Japanese abductees.

WSJ: Trip to Pyongyang Irks Tokyo's Allies