The United States urged North Korea on Monday not conduct a nuclear test or launch a satellite and called on China to exert its influence over its neighbor to try to ward off such "provocative actions."
North Korea, which is pressing ahead with plans for a satellite launch despite U.S. and regional appeals that it desist, is also preparing a third nuclear test, South Korean news reports said on Sunday.
Another nuclear test is bound to scare neighbors and infuriate the West, which has long sought to curb the North's nuclear ambitions.
South Korea's Yonhap news agency quoted an unidentified intelligence source as saying North Korea was "clandestinely preparing a nuclear test" at the same location as the first two.
The State Department repeated its advice to the North not to launch a satellite, saying this would violate U.N. Security Council resolutions and a Feb. 29 denuclearization agreement.
"Our position remains: don't do it," said spokeswoman Victoria Nuland. "North Korea's launch of a missile would be highly provocative, it would pose a threat to regional security and it would be inconsistent with its recent undertakings to refrain from any kind of long-range missile launches."
Nuland told reporters a third North Korean nuclear test "would be equally bad if not worse."
She declined comment on whether the United States also had reason to believe that the North might be preparing a nuclear test, saying she could not discuss intelligence matters.
North Korea, which three years ago pulled out of six-party disarmament talks on its nuclear program, agreed in February to stop nuclear tests, uranium enrichment and long-range missile launches in return for food aid, opening the way to a possible resumption of the negotiations.
But that has all unraveled with the North's rocket launch planned for this month, probably between Thursday and the following Monday. The North says it is merely sending a weather satellite into space, but South Korea and the United States say it is a ballistic missile test.
The United States has called on China, the closest that North Korea has to an ally, to exert such influence as it has with Pyongyang, a point Nuland made again on Monday.
"We believe, in particular, that China joins us in its interest in seeing a denuclarized Korean Peninsula and we are continuing to encourage China to act more effectively in that interest," she said.