North Korea has threatened to use force against any country that tries to stop it testing more missiles.

China, under pressure from Washington over North Korea's missile tests, said its chief negotiator would visit Pyongyang next week.

Pyongyang's statement came as the United States and Japan united against a UN Security Council split over whether to impose sanctions on North Korea for the missiles it fired on Wednesday.

North Korea's official KCNA news agency quoted a foreign ministry spokesman as saying: "The KPA will go on with missile launch exercises as part of its efforts to bolster deterrent for self-defence in the future.

"The DPRK will have no option but to take stronger physical actions of other forms, should any other country dare take issue with the exercises and put pressure upon it."

DPRK stands for the Democratic People's Republic of Korea.

Officials say North Korea launched at least six missiles from its east coast early on Wednesday and a seventh about 12 hours later.

The missiles included a long-range Taepodong-2, which some analysts had said could hit Alaska.

US officials said it flew for less than a minute and splashed into the sea west of Japan.

South Korea's defence minister told a parliamentary committee that an analysis of equipment and personnel being moved in and out of a missile-launch site in North Korea suggested the possibility of further launches.

The South Korean daily, Chosun Ilbo, cited a government official as saying the North might be looking to launch three or four more intermediate-range missiles.

NBC News, citing unnamed US officials, said preparations seemed to be under way for a second Taepodong test, but the weapon was not yet at the launch pad.

Analysts say it could take weeks to prepare a Taepodong-2 for firing. Tokyo said it did not expect an imminent launch.

Junichiro Koizumi, the Japanese prime minister, and the US president, George Bush, agreed to work together for a UN resolution demanding that nations halt funds and technology that could be used for Pyongyang's missile programme.

This agreement came after Russia and China opposed imposing sanctions on Noth Korea - echoing the split among the UN Security Council's veto-wielding members over Iran's nuclear ambitions.

Alexander Losyukov, the Russian ambassador to Japan, told reporters in Tokyo that sanctions could prevent a revival of six-country talks on ending Pyongyang's nuclear arms programme, which have been stalled since last November.

Christopher Hill, the US negotiator, said the launches had united opinion against Pyongyang, but he implied that Washington was seeking a tougher line from China.

"We need China to be very, very firm with their neighbours and frankly with their long-term allies, the North Koreans, on what is acceptable behaviour and what is not acceptable behaviour," Hill said.

The North Korean spokesman said Pyongyang did not feel bound by a ban on missile testing and had the right to conduct such tests in the interests of self-defence.

PHOTO CAPTION

A video grab shows a newsreader for North Korean official KRT state television reporting on July 6, 2006, a statement from the foreign ministry that North Korea had launched several missiles. (Reuters)