Singapore: US Secretary of State Condoleezza Rice said on Thursday after talks with North Korea that she believed Pyongyang was under no ‘illusions’ it had to agree to a strong mechanism to verify its nuclear activities.

On Wednesday, Rice joined ministers from South Korea, Russia, China and Japan in rare, ‘informal’ talks with North Korean's Foreign Minister Pak Ui-chun on the sidelines of a Southeast Asian forum.

‘I don't think the North Koreans left with any illusions about the fact that the ball is in their court and that everybody believes they have got to respond and respond positively on verification,’ Rice told reporters.

She said Wednesday's meeting - the first time a US foreign minister sat down with the North Koreans since 2004 - delivered a strong message that Pyongyang must quickly agree to the so-called verification protocol circulated earlier this month among the six parties.

Wednesday meeting's set the stage for a formal negotiating session when the ministers next meet in Beijing, China's Foreign Minister Yang Jiechi said. No date has been set for those talks, which previously had been at the envoy level.

In late June, the North presented a long-delayed account of its nuclear weapons programme that contained information on its plutonium production.

Rice said the declaration left open a lot of questions that needed to be answered with a strong verification mechanism. The declaration also did little to address US suspicions of a secret uranium enrichment programme.

‘Nobody is going to trust the North Korean number they have given on plutonium they made. Fortunately, there are very good tried and true nternationally-recognised methods to verify the number of kilogrammes of plutonium made,’ she said.

‘This will have to be specific, it will have to have specific measures, it will have to have means for access and it will also have to have means to continue this process as new information becomes available,’ she added.