MANILA - US Defence Secretary Robert Gates said Monday that North Korea could be preparing for a long-range missile test, but admitted that Pyongyang's intentions were not yet clear.

"We have seen some signs that they may be doing something with another Taepodong missile," Gates told a joint press conference with his Philippine counterpart Gilberto Teodoro.

"But at this point it's not clear what they're going to do," said the US defence secretary, who was making a flying visit to the Philippines on his way home from a regional security conference in Singapore.

A South Korean defence ministry spokesman on Monday told AFP that officials in Seoul had "detected signs that North Korea is preparing to fire an ICBM," or intercontinental ballistic missile.

The North has moved the missile to a base in Dongchang-ri along its northwestern coast and a launch could take place in one or two weeks, South Korea's Yonhap news agency quoted an unnamed intelligence official as saying.

Tensions have been running high for the past week after Kim Jong-Il's regime tested a nuclear bomb for the second time and then launched a series of short-range missiles and threatened possible attacks on South Korea.

Gates said he hoped a high-level US delegation led by Washington's special North Korea nuclear envoy Stephen Bosworth - due to meet with officials in China, Japan, Russia and South Korea - could help defuse those tensions.

"I would rather not presume that we will not be successful in gaining a broad agreement on the way forward," Gates told reporters.

"I think we ought to wait and see how those conversations go and how our partners in the six-party talks other than Pyongyang react to the developments of the last few weeks and see where we go from there diplomatically," he said.

He said he would rather "not speculate on what we might do after that."

The two Koreas, China, Japan, Russia and the United States make up a six-party forum that has been meeting for six years for negotiations aimed at ending Pyongyang's nuclear programmes.

Gates said at the weekend in Singapore that Washington would not accept a nuclear-armed North Korea, and that Pyongyang's defiant acts could spark an arms race with serous consequences for Asia.