Bush sends B-52s to Guam after North Korean jets buzz US spy plane

The United States is sending 24 B-1 and B-52 bombers to Guam in the western Pacific to deter any aggression by North Korea in case of a war in Iraq, the Pentagon said yesterday.

Officials described the deployment as a prudent measure to maintain peace on the Korean peninsula, where tensions have risen sharply over North Korea's threat to develop nuclear weapons.

They said it was not prompted by the interception of an American reconnaissance jet by North Korean fighters in international air space over the Sea of Japan on Sunday.

MiG fighters flew within 50 feet of the unarmed US aircraft, which they tailed for more than 20 minutes.

America said yesterday it would lodge a formal protest over the "particularly provocative" interception, the first such incident since the North Koreans shot down an American spy plane in 1969, killing 31 people on board.

Packed with high-resolution cameras with powerful telescopic lenses the RC-135 ­ known as the Cobra Ball ­ was almost certainly on a mission to spy on Pyongyang's ballistic missile systems. According to the Pentagon, four jets ­ two MiG-29s and two MiG-23s ­ flying 150 miles off the North Korean coast came as close as 15 metres and used radar to identify the American aircraft as a target. The spy plane broke off its mission and returned to Kadena air base in Japan.

There were expressions of concern from South Korea and China and angry words from Japan, whose chief cabinet secretary, Yasuo Fukuda, called the incident unacceptable.

The RC-135 is an information gatherer developed in the 1960s to spy on the Soviet Union. One of its principal tasks is to collect data on missile systems. This suggests it was on the lookout for signs that the North Koreans were preparing to test the Taepo Dong 2 ballistic missile, which America believes is capable of reaching its West Coast.

The North Koreans recently accused the United States of stepping up its spy flights in preparation for war, alleging that there were more than 180 cases of aerial espionage in February alone. Sunday's interception, unusual because North Korean pilots are rarely allowed to fly so far out of their airspace, was the latest in a growing list of challenges from President Kim Jong Il to the Bush administration.

In January, North Korea withdrew from the nuclear non-proliferation treaty and kicked out UN nuclear inspectors. It then moved to fire up nuclear plants capable of producing weapons-grade plutonium. The aim was to try to push Washington into talks in the hope that this would produce a non-aggression pact to secure North Korea's survival. The crisis erupted in October when America discovered that North Korea was secretly developing a uranium-enrichment programme, but some analysts believed it was triggered by President George Bush's inclusion of Pyongyang in his "axis of evil".

North Korea reiterated its demand for a non-aggression pact, saying it wanted "to remove the unreasonable US threat, not to gain something".

President Bush is sticking to his line of seeking a diplomatic solution without being seen to cave in to threats.