North Korea tells China of preparations for fresh nuclear test: Source

North Korea conducted third nuclear test , drawing global condemnation and a stern warning from the United States.

BEIJING: North Korea has told its key ally, China, that it is prepared to stage one or even two more nuclear tests this year in an effort to force the United States into diplomatic talks, said a source with direct knowledge of the message.

Further tests could also be accompanied this year by another rocket launch, said the source, who has direct access to the top levels of government in both Beijing and Pyongyang.

North Korea conducted its third nuclear test on Tuesday, drawing global condemnation and a stern warning from the United States that it was a threat and a provocation.

"It's all ready. A fourth and fifth nuclear test and a rocket launch could be conducted soon, possibly this year," the source said, adding that the fourth nuclear test would be much larger than the third, at an equivalent of 10 kilotons of TNT.

The tests will be undertaken, the source said, unless Washington holds talks with North Korea and abandons its policy of what Pyongyang sees as attempts at regime change.

North Korea also reiterated its long-standing desire for the United States to sign a final peace agreement with it and establish diplomatic relations, he said. North Korea remains technically at war with both the United States and South Korea after the Korean war ended in 1953 with a truce.

In Washington, US State Department spokesperson Victoria Nuland urged North Korea to "refrain from additional provocative actions that would violate its international obligations" under three different sets of UN Security Council resolutions that prohibit nuclear and missile tests.

North Korea "is not going to achieve anything in terms of the health, welfare, safety, future of its own people by these kinds of continued provocative actions. It's just going to lead to more isolation," Nuland told reporters.

The Pentagon also weighed in, calling North Korea's missile and nuclear programs "a threat to US national security and to international peace and security."

"The United States remains vigilant in the face of North Korean provocations and steadfast in our defense commitments to allies in the region," said Pentagon spokesperson Major Catherine Wilkinson.

Initial estimates of this week's test from South Korea's military put its yield at the equivalent of 6-7 kilotons, although a final assessment of yield and what material was used in the explosion may be weeks away.

North Korea's latest test, its third since 2006, prompted warnings from Washington and others that more sanctions would be imposed on the isolated state. The UN Security Council has only just tightened sanctions on Pyongyang after it launched a long-range rocket in December.

Pyongyang is banned under UN sanctions from developing missile or nuclear technology after its 2006 and 2009 nuclear tests.

North Korea worked to ready its nuclear test site, about 100 km (60 miles) from its border with China, throughout last year, according to commercially available satellite imagery. The images show that it may have already prepared for at least one more test, beyond Tuesday's subterranean explosion.

"Based on satellite imagery that showed there were the same activities in two tunnels, they have one tunnel left after the latest test," said Kune Y Suh, a nuclear engineering professor at Seoul National University in South Korea.

Analysis of satellite imagery released on Friday by specialist North Korea website 38North showed activity at a rocket site that appeared to indicate it was being prepared for a launch.