A senior Japanese diplomat on Friday urged North Korea to act to resolve the dispute over its nuclear weapons programs. His comments came just hours after U.S. officials said that North Korea had halted reprocessing spent fuel at its main nuclear facility.

Japanese Senior Vice Foreign Minister Toshimitsu Motegi says that Pyongyang should make the first move toward ending a standoff over its nuclear ambitions. In a speech on Friday, he also warned that time is working against the isolated Stalinist nation in the 11-month-old dispute over its nuclear programs.

His words come one day after American officials said that North Korea appears to have stopped reprocessing spent nuclear fuel at its Yongbyon nuclear facility. The reason for the halt remains unclear.

At the plant, which was restarted in February, spent nuclear fuel can be turned into plutonium, which can then be used in nuclear bombs. The plant also functions as a nuclear reactor.

U.S. officials also said Thursday that they believe the North is developing a new ballistic missile capable of reaching the United States.

Despite the U.S. comments, Mr. Motegi, the Japanese diplomat, says it is not likely that Pyongyang will carry out its threat to conduct nuclear tests.

He also says he is optimistic that a second round of six-country talks on the nuclear dispute might be held in late October. A first round of talks in Beijing was held last month with the United States, the two Koreas, China, Russia and Japan. It ended without concrete progress.

Japan's Kyodo news agency, citing anonymous Russian sources, reported Friday that North Korea has agreed in principle to attend a second round of talks in November. The report says North Korea has sent word to Russia, one of its few allies, on the decision.

Also on Friday, ships from the United States, Japan, France and Australia arrived in the western Pacific to start exercises simulating the interception of vessels suspected of carrying weapons of mass destruction.

The exercise is not aimed specifically at North Korea. But Derek Mitchell, an analyst with the Center for Strategic and International Studies in Washington, says it sends a clear message to Pyongyang that it must change its behavior. The United States and other nations accuse Pyongyang of shipping drugs, counterfeit money and missiles.

"You have to have both dialogue and a certain deterrent," he said. "The signals are important. I don't think there is any problem with sending certain signals saying both: we are ready to make deal but we are also ready for you if you are not willing to make a deal."

Also on Friday, North Korean official media repeated the government's position that it has no intention of giving up its nuclear programs. Its efforts to become a nuclear-armed power violate a number of international accords.