Syria 'had covert nuclear scheme'
The United States has accused North Korea of helping Syria build a nuclear reactor that "was not intended for peaceful purposes".
The site, said to be like one in North Korea, was bombed by Israel in 2007.
Syria must "come clean" about its secret nuclear programme, the White House said in a statement after CIA officials briefed members of Congress.
Syria has repeated denials that it has any nuclear weapons programme, or any such agreement with North Korea.
The construction of this reactor was a dangerous and potentially destabilising development for the region and the world
White House statement
But the White House said the "cover-up" operation that Syria carried out after the Israeli air strike reinforced the belief that the reactor "was not intended for peaceful activities".
"Until 6 September, 2007, the Syrian regime was building a covert nuclear reactor in its eastern desert capable of producing plutonium," the statement said.
"The Syrian regime must come clean before the world regarding its illicit nuclear activities."
The statement added that the US had long been "seriously concerned about North Korea's nuclear weapons programme and its proliferation activities".
But the White House insists it is committed to the on-going six-nation diplomacy, between North Korea and US, China, Japan, South Korea and Russia that led to a landmark deal with Pyongyang, in February 2007.
Ulterior motive?
North Korea agreed to give up its nuclear weapons in return for aid and its removal from a blacklist of state sponsors of terrorism. But the US has accused Pyongyang of missing the deadline to make a full nuclear declaration as promised.
The CIA briefing and statement coincides with the end of a two-day meeting between US and North Korean officials on Pyongyang's nuclear programme, which both sides say have gone well - fuelling speculation that a deal may be imminent.
The BBC's James Coomarasamy, in Washington, says the question being asked by some in the US capital is whether the reactor statement is designed to reinforce those diplomatic efforts or an attempt by some in the administration to undermine them.
Damning images?
The CIA briefings included pictures which the US says prove that North Koreans were working inside the secret site.
One of the images, which shows two men standing side by side, was said by the CIA to be of the head of the North Korean nuclear plant and the head of the Syrian atomic energy commission together in Syria.
The images - said to have been obtained by Israel - showed striking similarities between the Syrian facility and the North Korean reactor at Yongbyon, the US said.
However, the facility was not yet operational and there was no fuel for the reactor, officials said.
Israeli fears
Republican Congressman Pete Hoekstra, who attended the CIA briefing, said the US needed "good, clear, verifiable information" from the countries involved before North Korea could be removed from the terrorism blacklist, the AFP news agency quoted him as saying.
Mr Hoekstra criticised the Bush administration for waiting eight months to brief the intelligence committee and warned that it could jeopardise any future agreement with North Korea.
Syria's ambassador to the UN, Bashar Jaafari, denied the links.
"There was no Syria-North Korea co-operation whatsoever in Syria. We deny these rumours," he said.
North Korea has previously denied transferring nuclear technology to Syria.
The BBC's Katya Adler in Jerusalem says the apparent strike on the reactor, deep inside Syria, was seen by many in Israel as a sign of their military prowess.
But she says Israeli defence officials now have expressed concern over the revelation of classified data in the US.
BBC NEWS | Middle East | Syria 'had covert nuclear scheme'
I don't agree. I've heard this several times, and I don't agree.
