SEOUL ? Former US president George W. Bush Wednesday urged nations negotiating with North Korea to stay united to pressure the communist state into abandoning its nuclear ambitions.

Bush told a Seoul forum that Pyongyang is undoubtedly testing the six-nation negotiating process and the other members must not give in.

"I believe that the best way to bring peace to the Korean peninsula is multilateral diplomacy through the six-party talks," Bush said in a keynote speech to the World Knowledge Forum.

"The president of North Korea will, no doubt, test the system, and, no doubt, try to find weaknesses," he said, referring to leader Kim Jong-Il who is not in fact president.

"I'm confident the issue can be resolved peacefully when China, [South] Korea, Japan, Russia and the United States speak with one voice to say that there is a better way forward."

Early in his term Bush took a hardline stance with the North and famously labeled it part of an "axis of evil" in 2002.

But the following year he agreed to the creation of the six-party forum, designed to persuade Pyongyang to give up its nuclear programs in exchange for economic aid and major security and diplomatic benefits.

The latest six-party talks last December ended in stalemate and the North quit the forum in April. But Bush reiterated his faith in it as the best approach.

North Korea said last week it was willing to return to the six-party process, but only if it can first make progress in separate bilateral talks with the United States.