The meeting, set to begin at 4:40 pm Singapore time was already planned but is set to center on Pyongyang's moves that have drawn global condemnation.

'Undoubtedly, developments in North Korea over the weekend will be a focus of that conversation,' said Pentagon spokesman Geoff Morrell.

The trilateral meeting between Mr Gates, Japan's Yasukazu Hamada and South Korea's Lee Sang-Hee, will be the first between the defense ministers.

North Korea also reportedly fired two short-range missiles on Tuesday after its test of a nuclear device.

The UN Security Council held an emergency meeting to consider the options after Pyongyang's test of a nuclear device on Monday.

Susan Rice, US ambassador to the United Nations, has warned Pyongyang would 'pay a price' if it continued to carry out nuclear and missile tests in violation of international law.

'If you want to continue to test and provoke the international community, they're going to find they'll pay a price because the international community is clear: it's not acceptable,' Dr Rice said on CNN television, in reaction to Pyongyang test-firing two short-range missiles on Tuesday.

The tough words from Washington came a day after the UN Security Council unanimously condemned North Korea for testing a nuclear bomb Monday, as major powers mulled fresh punitive action and US President Barack Obama pledged support to Pyongyang's neighbors.

'You heard the entire international community yesterday from various capitals and from the security council come out swiftly, forcefully, and in unity to condemn' the tests, Dr Rice said.

'We agreed yesterday we're going to pursue in the security council a new resolution - a strong resolution with teeth,' she said, adding that sanctions 'could take very different forms' and might include 'economic levers'. -- AFP, AP