The UN's nuclear chief today criticised the US for the delay in publishing what Washington claims is proof that a Syrian nuclear reactor was built with help from North Korea.

Mohamed ElBaradei, the head of the International Atomic Energy Agency, was briefed yesterday by the US under-secretary of state for arms control, shortly before the director of the CIA, Michael Hayden, briefed members of Senate and House committees on the same intelligence.

"The director general deplores the fact that this information was not provided to the agency in a timely manner, in accordance with the agency's responsibilities under the nuclear non-proliferation treaty, to enable it to verify its veracity and establish the facts," ElBaradei said in a statement today.

He was critical of Israel's bombing of the site of the alleged reactor. "The director general views the unilateral use of force by Israel as undermining the due process of verification that is at the heart of the nonproliferation regime," the statement said.

The Pentagon released a video yesterday it claimed was proof North Korea had helped Syria to build a secret nuclear reactor and called it "a dangerous and potentially destabilising development for the region and the world".

Today, Syria accused the US of complicity in the Israeli bombing raid which destroyed the site. "The US administration was apparently party to the execution of the September raid by Israeli warplanes on eastern Syria," a statement said.

The White House said Israel had consulted the Pentagon before launching the strike, but that it did not give a "green light" to the air raid.

After the Israeli attack last September, there was speculation that the target was a nuclear reactor, but this is the first time there has been an official statement. It was also the first time North Korea has been mentioned in the affair.

The White House spokeswoman, Dana Perino, speaking after the Senate and House of Representatives had been briefed, said yesterday Syria had built the plant "carefully hidden from view" in a remote desert area in the east of the country, in breach of its international obligations.

"We are convinced, based on a variety of information, that North Korea assisted Syria's covert nuclear activities. We have good reason to believe that the reactor, which was damaged beyond repair on September 6 of last year, was not intended for peaceful purposes," she said.

The White House added that the regime moved quickly to bury evidence of its existence, covering over the wreckage and constructing a new building on the site. US officials said the Bush administration was putting the information out in order to clear the decks before doing a deal with North Korea to dismantle its nuclear programme.

The video, made public last night after Congress had been briefed, is a collection of material from various sources, in addition to Israeli intelligence. There is no tape from inside the alleged reactor, only two still photographs, apparently taken by a person on the ground rather than a drone or satellite. This was supported by satellite pictures and graphs.

The pictures taken on the ground show an apparently empty brown-grey, building, but nothing that seems to indicate it is being used for nuclear purposes.

In the video, which shows the site before and after the bombing, the CIA claims that the alleged reactor is similar to one in Yongbyon, 55 miles north of the North Korean capital, Pyongyang.

One official said the Syrian plant was within weeks or months of being operational. "This thing was good to go," he said. Congress was told that the reactor was designed to produce a small amount of plutonium, which can be used to build a nuclear bomb.

In releasing the video, the Bush administration is taking the risk that North Korea may use it as an excuse to walk out of negotiations about dismantling its nuclear programme, but is banking on any such action as being only temporary.

Under a deal agreed last year between North Korea, the US, China, Japan, South Korea and Russia, Pyongyang is required to detail whether it has provided nuclear help to Syria and other countries round the world. So far it has failed to deliver.

A US official who had seen the video said: "We cannot move forward [on a deal with North Korea] unless you acknowledge we are doing this with our eyes wide open. And we are going ahead with our eyes wide open."

The Syrian government yesterday denied it had been building a nuclear reactor with North Korean help. Syria's ambassador to Britain, Sami al-Khiyami, described the video as ridiculous: "Unfortunately the scenario of taking and retaking pictures looks like what happened before the Iraq war, when the US administration was trying to convince the world that Iraq had nuclear weapons."

In the run-up to the invasion of Iraq, the Bush administration showed photographs and other material to the UN security council that it claimed amounted to evidence of Saddam Hussein's pursuit of weapons of mass destruction, but the claims were subsequently proven to be false.

Joseph Cirincione, an expert on nuclear proliferation and head of the Washington-based Ploughshares Fund, said: "We should learn first from the past and be very cautious about any intelligence from the US about other country's weapons."