In an unusually strong attack, a foreign ministry spokesman slammed Bush for calling North Korean leader Kim Jong-Il a tyrant during campaigning last Wednesday in Wisconin.

The spokesman said hostile US policy would make it impossible for North Korea to attend six-nation working-level talks on the nuclear issue, which had been scheduled for August but have yet to materialise.

"He is a political imbecile bereft of even elementary morality as a human being and a bad guy," said the spokesman, quoted by the official KCNA news agency.

The spokesman accused Bush of trying to topple the legitimate government of North Korea, branding him "a tyrant that puts Hitler into the shade" as well as "an idiot, an ignorant, a tyrant and a man-killer."

He said that following Bush's comments, North Korea could not attend working-level discussions aimed at paving the way for a new round of ministerial negotiations on the nuclear issue. The talks bring together the two Koreas, China, Japan, Russia and the United States.

"This made it quite impossible for the DPRK to go to the talks and deprived it of any elementary justification to sit at the negotiating table with the US," said the spokesman.

Bush said last week that he had brought together China, Japan, South Korea and Russia to pressure Pyongyang. "So there's now five countries saying to the tyrant, disarm, disarm," he said.

North Korea's angry response came as US and South Korean troops Monday began 12 days of annual military exercises to test their response to a possible invasion by North Korea.

The North insists the exercise is part of Washington's war preparations to topple the Stalinist regime. The operation, called Ulchi Focus Lens, involves over 14,500 US troops.

The North Korean reaction has fueled new concerns over the six-nation talks process which has so far failed to make headway in defusing the standoff over Pyongyang's nuclear programmes.

The United States wants North Korea to close down all its nuclear weapons facilities in return for a package of economic and diplomatic rewards.

Washington also said it would give North Korea security guarantees that it would not be attacked. The United States has no diplomatic ties with North Korea, which is also on the US list of countries sponsoring terrorism.

North Korea rejected the proposals and said it wanted aid and guarantees before it went ahead with freezing its nuclear programs.

The stand-off over the North's quest for nuclear weapons erupted in October 2002 when Washington accused Pyongyang of operating a secret nuclear program based on enriched uranium in violation of a 1994 freeze of its separate plutonium producing program.

Pyongyang has denied running the uranium-based program, but has again fired up its once-mothballed nuclear reator to extract plutonium. The CIA estimates it has at least one or two nuclear bombs.

After the last round of talks in Beijing in June, host China said there was an agreement in principle for a new round of talks by the end of September. However analysts have questioned whether either the United States or North Korea would want new negotiations before November's US presidential election.

However South Korea said it would keep pushing to keep the process alive.

A South Korean delegation led by Deputy Foreign Minister Lee Soo-Hyuk is to visit Tokyo and Beijing this week to discuss a timetable for a new working-level dialogue.

WAR.WIRE