"Obviously, there are some really tough issues we're going to take up in Beijing," Hill said after meeting his Japanese counterpart Akitaka Saiki as part of his preliminary contacts ahead of the talks starting Monday.

"As we consider these difficult issues, verification and things like that, we want to make sure that the US and Japan are very close together," he said.

"I think the US and Japan are working very, very closely together and we have a very strong understanding on what needs to be accomplished."

Saiki said he also expected the Beijing talks to "face a difficult situation."

"It is extremely important to form a six-nation agreement in writing which gives no room for misunderstandings and distorted interpretations as to the methods of verification as well as facilities and programmes to be verified," he said.

Hill, the US assistant secretary of state for East Asian and Pacific affairs, and Saiki, director of Asian and Oceanian affairs at the Japanese foreign ministry, will meet again here on Wednesday, joined by South Korean nuclear envoy Kim Sook.

Hill said he would then go to Singapore and meet his North Korean opposite number, Vice Foreign Minister Kim Kye Gwan, during his stay there before heading to Beijing on Sunday.

He said the opinions of the US, Japan and South Korea "are very much in synch."

Russia is also party to the five-year-old six-nation talks aimed at dismantling North Korea's nuclear arsenal in exchange for economic and diplomatic benefits.

US Secretary of State Condoleezza Rice has said the heads of the six delegations should aim to finalise a plan allowing for outside verification of the communist North's disarmament.

The United States struck North Korea off a terror blacklist on October 11 after saying that Pyongyang had agreed to steps to verify disarmament and pledged to resume disabling its atomic plants following a hiatus lasting several months.

However, North Korea disputes a US claim that it agreed to the removal of samples from its nuclear facilities. It said that external verification of its nuclear inventory will involve only field visits, confirmation of documents and interviews with technicians.

The US State Department has insisted that sampling is part of the deal that Hill reached during a visit to Pyongyang on October 1-3, although it would not say whether anything was committed to paper.

Rice has said she wanted a "protocol" to be signed in Beijing to detail the steps of verification.

"The important point to understand is that when we get to verification we don't want misunderstandings," Hill said. "And the way to clear up misunderstandings is to have things worked out in advance, and that's what the protocol is all about."