The chief US envoy on North Korea is due to arrive in Tokyo, for talks on how to move forward after Pyongyang's reported nuclear test last week.
Christopher Hill is at the start of a tour of Asia
Christopher Hill will focus on how the US and Japan can co-operate to enforce UN sanctions against Pyongyang.
On Saturday the UN Security Council approved a resolution that imposed both weapons and financial sanctions.
But despite the unanimous vote, disagreements are already emerging between the members of the council.
Beijing has indicated that it still has reservations about carrying out the extensive cargo inspections that Washington says are called for in the resolution.
But the US ambassador to the UN, John Bolton, said China had an obligation to comply with the resolution.
Mr Hill is expected to spend two days in Tokyo, focusing on US-Japan co-operation over the North Korean crisis.
Japan is looking at whether it can provide logistical support for US vessels if they start trying to inspect cargo ships going to or from North Korea.
The Security Council... condemns the nuclear test proclaimed by the DPRK on 9 October 2006 in flagrant disregard of its relevant resolutions
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The restrictions imposed by Japan's pacifist constitution may require the government to pass new laws to allow that to happen.
In a further diplomatic drive, US Secretary of State Condoleezza Rice is due to arrive in Japan on Wednesday.
She reportedly intends to reassure the country that Washington will provide adequate protection in the event that North Korea obtains a viable nuclear weapon - a message she will later take to South Korea.
The UN resolution against North Korea was agreed on Saturday after lengthy negotiations.
It imposes tough weapons restrictions, targets luxury goods and imposes a travel ban on some North Korean officials.
It also allows the inspection of cargo vessels going in and out of North Korea for banned materials, although the resolution was weakened slightly at China and Russia's insistence, to make this provision less mandatory.
Beijing's UN envoy, Wang Guangya, said immediately after the vote that China urged countries to "refrain from taking any provocative steps that may intensify the tension".
Both Russia and China are concerned that inspections could spark naval confrontations with North Korean boats.
Mr Bolton said China had a "heavy responsibility"
But Mr Bolton told American television that China had voted for the sanctions and therefore "China itself now has an obligation to make sure that it complies."
"China's got heavy responsibility here," he said.
North Korea has reacted angrily to the resolution. Its UN envoy, Pak Gil-yon, condemned the move before storming out of the meeting in New York.
The isolated communist state announced on 9 October that it had carried out an underground nuclear test in Gilju in Hamgyong province.
US officials said on Saturday that preliminary results of scientific tests appeared to confirm that that claim was true, but they stressed that more tests were needed to reach a conclusion.