Discovery of radioactive air 'may confirm' nuclear test

US officials have found traces of radioactive air which may confirm that North Korea did carry out a nuclear test as it claimed on Monday.

Preliminary results of the test revealed a type of radioactive gas that would have been present after a nuclear detonation.

However, the sample analysis is not definitive or conclusive, officials warned.

A senior Bush administration official said: “The betting is that this was an attempt at a nuclear test that failed.

“We don’t think they were trying to fake a nuclear test, but it may have been a nuclear fizzle.”

Since North Korea’s announcement that it had tested a nuclear bomb, the United States and other nations have been conducting scientific tests to determine whether a nuclear explosion had occurred.

One congressional official said that radioactive material was found in an air sample collected on Wednesday.

Results from another test disclosed yesterday showed no evidence of radioactive particles that would be expected from a successful nuclear detonation, a US government intelligence official said.

The Chinese and Japanese governments have done their own air sampling and found no trace of radioactive material.

At the White House, press secretary Tony Snow said the Bush administration’s analysis of the North Korean explosion was continuing.

“They still think the analysis that they’re doing will take another day or two,” he said.

Analysts and government officials have said it may take weeks or longer to determine whether the North Korean explosion was nuclear.

Daryl Kimball, executive director of the private Arms Control Association, said: “Sampling devices may simply have been in the wrong place at the wrong time, or the amounts of radioactive material may have been too small to detect because this may have been a failed test of a small nuclear device.”

The air sample was taken on Tuesday by a specialised aircraft, the WC-135, flying from Kadena Air Base in Okinawa, Japan.

It apparently took the sample over the Sea of Japan, between the Korean mainland and Japan.

Members of the UN Security Council agreed yesterday on the wording of a resolution that would clamp sanctions on the communist country.

The draft, scheduled for a vote tomorrow, would authorise non-military sanctions against the North and says that any further action the council might want to take would require another UN resolution.

It also eliminates a blanket arms embargo from a tougher, previous draft, targeting instead specific equipment for sanctions including missiles, tanks, warships and combat aircraft.

Meanwhile, US Secretary of State Condoleezza Rice will travel to China, South Korea and Japan next week to discuss steps to pressure North Korea to drop its nuclear efforts and to assess the region’s security situation.

Rice’s trip is the next step in the US diplomatic offensive at the United Nations and with North Korea's neighbours.

Rice’s trip is meant to present a unified front to North Korea, which will be looking for any cracks in the diplomatic coalition behind the UN statement.

Coming less than a month before congressional elections in the United States, Rice’s trip also provides an opportunity for the Bush administration to highlight its work countering dangerous regimes and terror threats.

Beyond the threat to Asian neighbours and perhaps other nations posed by a nuclear North Korea, the Bush administration is worried that Pyongyang could sell its nuclear expertise to terrorists or other potential US enemies, including Iran.

Assistant Secretary of State Christopher Hill said: “Now is the time really to be very firm – to be calm, but firm – and to make clear to the North Koreans that no one is going to accept them as a nuclear weapons state, that we’re not going to live with them as a nuclear weapons state, that they’re going to have to get themselves out of this category and join in the world and choose another path.”