"I think it would be very unfortunate if the North Koreans were to do something like this and break out of the moratorium that they have been following for a number of years," Powell said.

News of a possible test emerged from Seoul on Thursday where South Korean Defense Ministry spokesman Nam Dae-Yeon said South Korean and US military authorities had recently noticed "missile-related activities" in North Korea.

"We cannot rule out the possibility of the North test-firing missiles," Nam said.

Powell said he was aware of intelligence reports to that effect but stressed he could not predict what Pyongyang might do.

"I have seen some indications of activity but I can't be sure what it means," he told reporters at the State Department's Foreign Press Center here.

While acknowledging the "strong concerns" that any test would register among North Korea's neighbors, Powell stressed it would trigger no change in US policy.

"It would not change our approach to dealing with the North Korea nuclear problem," he said. "We would stay very firmly embedded in the six party framework and we would not be intimidated with respect to policy."

"I think it would be a very troubling matter though, for China and Russia and Japan and South Korea, who are in range of such missiles," Powell added.

Nam said South Korean and US authorities were "closely following" the situation, even as some other South Korean officials suggested that the activities in question might be nothing more than routine military drills.

"Recently activities related with missiles have been detected and it's highly likely that it could be a routine and annual exercise," Vice Unification Minister Rhee Bong-Jo said.

Yonhap news agency quoted an intelligence source as saying that military vehicles, soldiers and missile experts were converging around a launch site for the North's Rodong missile which has a range of some 1,300 kilometresmiles).

The source told Yonhap that the test was more likely to be a command post simulation than a real test-firing. North Korea carried out test-firing simulations two years ago.

In Tokyo the Yomiuri Shimbun newspaper said US and Japanese authorities had determined from satellite images and radio traffic that North Korea was preparing to launch a Rodong missile.

Pyongyang stunned the world in August 1998 by test-launching over Japan a Taepodong-1 missile with a range of up to 2,000 kilometers, claiming it was a satellite launch.

Pyongyang declared a moratorium on missile tests in September 1999 and in May 2001 extended the decision until 2003.

The cash-strapped country, however, has refused to stop missile exports, a major source of hard currency earnings.

In addition to delivering the warning on missile tests, Powell urged Pyongyang to stop delaying the start a new round of multiparty talks on ending the crisis over North Korea's nuclear weapons programs.

He noted that Russian President Vladimir Putin had on Wednesday called for a resumption in the so-called "six-party talks" between China, Japan, North and South Korea, Russia and the United States.

North Korea has balked at returning to the table for another round of talks by the end of this month as planned and the other members of the six-party process have admitted the talks were unlikely to take place on schedule.

"It's hard to predict what the North Koreans are waiting for," Powell said, speculating that Pyongyang might be hoping for a change in US leadership from November's presidential election.

"But what is absolutely clear is that six-party talks are the way forward, there is no other plan, there is no substitute for the six-party talks." he said.

"We hope that the North Koreans will realize that as soon as they return to the six-party format and begin discussions again at the fourth round of the six-party meeting, the sooner we will be able to help North Korea deal with its very serious economic problem."

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