The White House yesterday broke seven months of silence over why Israel bombed a building in the Syrian desert last year, saying that it was convinced North Korea was helping to build a nuclear plant at the site.

In a statement issued last night, President Bush’s press secretary declared the collaboration between Syria and North Korea represented “a dangerous and potentially destabilising development for the world” because the facility was unlikely to have been for “peaceful purposes”. Syria described the accusation as “absurd”.

Hours earlier the CIA had finally given Congress sight of videotapes and other “extremely compelling” evidence which, it believes, indicates that North Korea was helping Syria. The nuclear plant was destroyed by an Israeli airstrike on September 6 that has since been the focus of world-wide speculation.

Intelligence officials showed committees on Capitol Hill a video taken inside the Syrian al-Kibar facility in which Korean faces were said to be visible. The design of the plant is alleged to resemble the North Korean reactor at Yongbyon, including a similar configuration and number of holes for fuel rods.

The CIA believes the facility would have been capable of producing plutonium for nuclear weapons but was destroyed by the Israelis just weeks before it became operational. The air strike last year has been compared to the raid on Iraq’s Osirak reactor in 1981. The videotape is understood to have been provided by Israeli intelligence hoping to overcome US scepticism, but the CIA yesterday stressed it had material from different sources that also pointed to North Korean involvement.

Syria’s Ambassador to the US condemned the disclosures and insisted once again that his country never had a nuclear programme. Imad Moustafa said: “This is exactly the same story as Iraq and its weapons of mass destruction. There is a proven record of this [US] Administration to fabricate lies.”

But both the US and Israel feared that if the Syrian reactor had become operational, not only would an Arab nation have developed nuclear capability for the first time but also that the regime the Washington accuses of supporting terrorism could have obtained weapons of mass destruction.

Yesterday’s disclosures came at a sensitive time for relations between the US and North Korea. The US State Department is pressing Pyongyang to come clean about the full extent of its nuclear programme – including exporting such technology – before lifting sanctions against a country which Mr Bush once proclaimed was part of an “axis of evil”.

But national security hawks have criticised the US Administration for watering down previous demands that North Korea publicly admit to having a nuclear weapons programme and helping Syria.

Dick Cheney, the Vice-President, is among those believed to be concerned that North Korea is being rewarded for “bad behaviour”, and there has been speculation that the release of intelligence material is designed to wreck the six-party talks on disarmament that represent one of the few achievements of multilateral diplomacy in recent years.

Congressional resistance to the compromise deal with North Korea probably prompted yesterday’s disclosures. Peter Hoekstra, the senior Republican on the House of Representatives Intelligence Committee, complained repeatedly about the “unprecedented veil of secrecy” thrown around the September airstrike.

Yesterday he appeared little mollified, saying that by waiting so long to reveal intelligence material “the Administration has made it much more difficult – if they do reach some kind of agreement with the six-party talks – for them to go through the Congress and get these agreements approved”.

Both the US State Department and the North Korean Government said that talks in Pyongyang on the nuclear issue this week were making progress despite the latest row.

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