However some lawmakers said the claims could wreck vital six-party talks on North Korea's nuclear programme.
 
"By waiting so long to be briefing the intelligence committee and other committees ... the administration has made it much more difficult that if they do reach some kind of an agreement with the six-party talks," said Pete Hoekstra, the top Republican on the House of Representatives Intelligence Committee said.
 
"It will be much harder for them to go through the Congress and get these agreements approved."
 
'Damning' evidence
 
Last September an Israeli air raid destroyed a target in Syrian territory which some reports said was a nuclear facility being built with North Korean help.
 
UN nuclear watchdog chief Mohammed
ElBaradei has reportedly been briefed [EPA]
Syria, a signatory to the nuclear Non-Proliferation Treaty (NPT), has maintained in the past that the site was an unused military facility, later razed the site and built a larger building in its place.
 
The target of Israel's raid has been veiled in secrecy, with US intelligence and government officials refusing to confirm for months that such a raid even took place.
 
US intelligence officials told the Washington Post that intelligence chiefs planned showing US legislators video presentation including stills which, they said, showed the alleged Syrian reactor had a core design similar to the North Korean reactor at Yongbyon.
 
The design included an identical configuration and number of holes for fuel rods and showed "remarkable resemblances inside and out to the North Korean plant", the official told the paper.
 
One nuclear weapons specialist also told the paper the video was "very, very damning".
 
However, Imad Moustapha, the Syrian ambassador to the US, denounced the allegations to the newspaper.
 
"If they show a video, remember that the US went to the UN Security Council and displayed evidence and images about weapons of mass destruction in Iraq," he told the Post.
 
"I hope the American people will not be as gullible this time around."
 
Sensitive timing
 
Joseph Cirincione, an expert on nuclear proliferation, told Al Jazeera that North Korea was the target of the briefing, as "very few officials ... are actually worried that Syria had then or does have now a programme that would threaten the US and Israel."
 
"There are conservatives in the US who don't like the terms of the deal the US has worked out, they think it's a little too weak," he says.
 
"There are others, such as the neo conservatives Dick Cheney, John Bolton ... who don't like any agreement and who don't want to set a precedent of negotiating with a tyrannical regime [North Korea] for fear that it would set a precedent for the US negotiating with Iran," he adds.
 
In addition to the US briefing, John Rood, acting under secretary for arms control and international security, briefed Mohamed El Baradei, who heads the International Atomic Energy Agency (IAEA), about the details being presented to Congress, US officials told AFP news agency.
 
The allegations of Syrian-North Korean nuclear co-operation come at a sensitive time for Pyongyang, which reached agreement over its nuclear weapons program last year in six-party talks with the US, China, Japan, South Korea and Russia.
 
On Tuesday a delegation of US nuclear experts travelled to North Korea for talks with top officials on the nuclear issue and are expected to report back to Washington on Friday.