MOSCOW - Russia's top envoy to North Korea said on Friday that any attempt by the U.N. Security Council to slap economic sanctions on Pyongyang over its nuclear programme would be seen by the isolated state as a declaration of war.

Russian Deputy Foreign Minister Alexander Losyukov, speaking after a trip to Pyongyang which included six hours of talks with North Korean leader Kim Jong-il, told reporters it was too early to take the nuclear stand-off to the Security Council.

"We have not exhausted diplomatic opportunities. Our talks in Pyongyang show that such opportunities exist," he said.

"To take this to the Security Council now would be seen by North Korea as an attempt to intensify pressure. And if talk is of economic sanctions, then this would simply be taken as a declaration of war."

U.S. Undersecretary of State John Bolton said in Tokyo on Friday that Washington was optimistic that the U.N. nuclear watchdog would refer the issue to the Security Council.

Losyukov, Russia's top Korea expert, flew to the isolated communist state last week to press for a solution to the crisis.

Russia, while steering clear of any official role as mediator in the row, has said it would use its Soviet-era ties to North Korea to encourage dialogue.

Russia is the only member of the Group of Eight leading industrialised countries with ties to both sides of the divided Korean peninsula. But diplomats said Moscow is far from certain how much clout it wields in the Stalinist state.

Russia has proposed a three-pronged solution to the stand-off, which includes safety guarantees for Pyongyang in exchange for North Korea dropping its nuclear weapons programme as well as a list of "small steps" both sides must take to defuse tensions.

"Our mediation efforts were on the whole rather successful. But this does not mean a solution to the crisis. It is more an indication of how to go about resolving it," he said.

President Vladimir Putin briefed U.S. President George W. Bush on the trip on Thursday, and Foreign Ministry officials said Japanese and South Korean officials were also informed.

"It is hard for the United States to take the first step, as it is for North Korea," he said. "So it is up to third countries to take steps for this dialogue to come about in the near future, even in the next few days."