"For the sake of peace and tranquility and stability in the Far East, Kim Jong-Il must listen," Bush said as he hosted a summit with Canadian Prime Minister Paul Martin and Mexican President Vicente Fox.

"If you want the way forward, if you want to be accepted by the world, if you want not to be isolated, get rid of your weapons programs," said the president, who was spending the week at his ranch in nearby Crawford.

Bush said US Secretary of State Condoleezza Rice had given him a two-hour briefing on her recently completed trip to Asia and denied that the chief US diplomat had set a deadline for the stalled talks to resume.

"I'm a patient person. And so are a lot of people that are involved in this issue. But the leader of North Korea must understand that when we five nations speak, we mean what we say," said Bush.

"And fortunately, it's not just the United States of America saying that," the president said, referring to the US partners in the talks -- China, Japan, Russia, South Korea.

"When the president said 'patient,' he was referring to any sort of June deadline. He was saying we have not set any deadline," White House spokesman Scott McClellan told AFP via email.

North Korea continues to say it will return to negotiations only if the conditions are right -- meaning the United States has to sweeten its offer on the table.

But Washington has ruled out giving any new incentives upfront to Pyongyang in return for disarmament, apart from endorsing a multilateral security guarantee and energy aid by the Stalinist state's neighbors.

Three rounds of talks have been held, but North Korea has refused to attend the fourth round scheduled last September and continues to shun the discussions.

"The president believes now is the time for North Korea to come back to the talks. We have a proposal on the table and it is time to talk about how to move forward on it," said McClellan.

Rice, who held meetings last week with Chinese, South Korean and Japanese leaders, has warned that North Korea faced "problems" if it failed to return to the six-party talks and that Washington was looking at "other options."

At the same time, Rice stressed: "We have no intention to attack."

On Monday, McClellan warned that diplomatic efforts cannot "drag on forever."

This was seen by analysts as a strong hint that Washington might resort to sanctions against the hardline communist state, a move that was flatly rejected by veto-wielding powers Moscow and Beijing three years ago.

North Korea last took part in the talks in June 2004. It declared on February 10 that it has nuclear weapons and that it was indefinitely suspending its participation in the dialogue.

A senior State Department official, who spoke on condition of anonymity, expressed concern Monday over what he called "a decided lack of movement" in the talks and difficulty in reading North Korea's intentions.

"I think we're concerned that as this drags on, the threat is not being reduced, and that gives a certain sense of urgency to what we are trying to accomplish," the official said.

But he added, "We're not yet at the point where we believe that the six-party talks is anything but the preferred way to go."