US Assistant Secretary of State Christopher Hill is surrounded by reporters upon arrival at Narita international airport, near Tokyo, Monday, September 4, 2006

The top U.S. negotiator has arrived in Japan with a warning that it may be difficult to revive talks on North Korea's suspected nuclear weapons. 

The U.S. assistant secretary of state for East Asia returned to the region Monday for consultations with Japanese, South Korean and Chinese diplomats about North Korea's nuclear program.

Christopher Hill, speaking to reporters at Narita International Airport outside Tokyo, said he was not optimistic about a quick resumption of six-way talks on North Korea, which have not been held for nearly a year.

"It's very clear we're in a very difficult period with the six-party process," he said. "The D.P.R.K. has not indicated any interest, right now, in returning to the process."

Hill's visit comes as concerns mount that North Korea, also known as the D.P.R.K., may be preparing to conduct its first nuclear weapons test. North Korea has declared it has such weapons.

A year ago, Pyongyang vowed to give up its nuclear program in exchange for security guarantees and much-needed foreign aid. However, it has refused to return to talks, because of U.S. sanctions imposed on some of its overseas businesses.

Washington contends the businesses are used to launder money and are tied to other criminal activities.

The Pyongyang government in July caused regional alarm by test-firing seven missiles.

Hill had no comment on speculation North Korea might conduct more such tests this Saturday when it marks its 58th anniversary as a nation.

Besides the two Koreas, Japan and the United States, the six-party talks also include host China and Russia.

Hill is to visit Beijing later this week, and is scheduled to hold talks in Seoul starting September 11. That will be just three days before South Korean President Roh Moo-hyun goes to Washington for a summit with President Bush.