Japanese Foreign Minister Nobutaka Machimura has again warned North Korea to return to nuclear talks or face being taken to the UN Security Council.

He was speaking on the sidelines of an Asia-Europe meeting (Asem) being held in the Japanese city of Kyoto.

The warning came amid fresh reports of intelligence suggesting North Korea may be about to test a nuclear weapon for the first time.

The North has not taken part in multinational talks for almost a year.

"If there is no progress, we have to think of other options, such as taking this matter to the United Nations Security Council," Machimura told reporters after meeting his South Korean counterpart, Ban Ki-moon.

Analysts say that taking North Korea to the UN could result in international sanctions against the impoverished nation.

North Korea has repeatedly said it would consider sanctions tantamount to a declaration of war.

Possible test

Machimura was speaking amid mounting concern that North Korea might be preparing a nuclear weapons test.

The New York Times reported on Friday that US officials were assessing satellite photographs that appeared to show extensive preparations for a test, which would confirm North Korea's claim to have developed nuclear weapons.

The New York Times said photographs suggested the digging and filling in of a tunnel in the country's remote north east, and the construction of a viewing stand.

Analysts cautioned, however, that assessing North Korea's real intentions is always difficult, and satellite photographs have been unreliable in the past.

Earlier on Friday, South Korean Foreign Minister Ban Ki-moon tried to persuade his Chinese counterpart, Li Zhaoxing, to use Beijing's influence on North Korea to bring it back to the talks table.

But according to Park Joon-woo, South Korea's director general in charge of Asia and Pacific affairs, Li stressed China's influence was "limited".

PHOTO CAPTION

North Korean People's Army soldiers take their position on guard in this undated photo. (REUTERS)