Pyongyang has boycotted talks on dismantling its nuclear program for more than a year over a dispute involving North Korean funds seized at a Macao-based bank.
Top U.S. nuclear envoy Christopher Hill said the disputed funds had now reached the North Koreans.
"My understanding is that today, it was deposited in a North Korean account in Russia," Hill told reporters on his arrival in Tokyo.
State media in the North had yet to confirm the deposit.
Meanwhile, North Korea, which often alternates concessions with harsh rhetoric and military actions that provoke international criticism, on Tuesday fired a short-range missile into waters toward Japan.
A South Korean intelligence official, who declined to be named, said the missile was launched in the afternoon and had a range of about 62 miles. It was the third such launch since late May.
Officials in the region reacted calmly.
"There is no circumstantial evidence that the missile launch is having a negative impact on the six-way talks and the resolution of the nuclear issue," said South Korean Foreign Ministry spokesman Cho Hee-yong.
The Japanese government sees the missile test a part of a routine drill and does not consider it a threat to national security, said a Foreign Ministry official in Tokyo, who spoke on condition of anonymity, citing the sensitivity of the matter.
Hill called Tuesday for Pyongyang to seal up its main reactor quickly once U.N. nuclear inspectors start assessing the facility next week.
Next week's trip by the International Atomic Energy Agency will be the first concrete step toward dismantling North Korea's nuclear program after a weekend breakthrough in the financial dispute that has delayed implementation of a disarmament accord.
The Vienna-based IAEA said it would send inspectors to the North next week, possibly as early as Monday, to discuss how to monitor and verify the shutdown of the Yongbyon nuclear reactor, as agreed by Pyongyang under the February agreement.
Under that deal reached in Beijing with China, Japan, Russia, South Korea and the United States, North Korea had pledged to shut down the reactor by the middle of April.
There is no new deadline set, however, for Pyongyang to carry through the pledge after the first deadline was missed.
Hill, on a regional tour to Beijing, Seoul and Tokyo, has said he hopes to see a shutdown "within weeks, not months."
Russia's Interfax-China news agency cited an unidentified North Korean official on Monday as saying Pyongyang plans to shut down the reactor in the second half of July.
"Again, we're going to really have to pick up the pace if we're to get back on our timelines," Hill said, stressing the need to make up for time lost due to the banking dispute.
The envoy said he said he has been in contact with the IAEA and it understands the "need to move quickly."
In Washington, Secretary of State Condoleezza Rice welcomed as "indeed a good step" North Korea's invitation of the IAEA team. "We expect North Korea to carry through with its obligations," she said.
The process of persuading North Korea to give up its nuclear program was stalled for months by a dispute over about $25 million in North Korean funds that were frozen in a Macau bank backlisted by the United States.