The destruction of a suspected Syrian nuclear reactor last year was the result of an intelligence collaboration that included a "foreign partner" who first identified the facility's purpose, CIA Director Gen. Michael Hayden said on Tuesday.

The reactor at the desert outpost of Al-Kibar was flattened in an air strike on September 6, 2007 that senior U.S. intelligence officials have said was carried out by Israel on its own initiative.

"Our foreign partnerships ... were critical to the final outcome," Hayden said in a speech for delivery to the World Affairs Council of Los Angeles.

A U.S. intelligence official declined to specify the partner Hayden referred to or to say whether it was Israel. He said there have been no signs that Syria was trying to replace the destroyed reactor.

Israel has never given an account of the strike or formally confirmed that it took place and some Israeli officials have quietly voiced dismay at U.S. disclosures about the strike.

"We were able last year to spoil a big secret, a project that could have provided Syria with plutonium for nuclear weapons," Hayden said.

Syrian President Bashar Assad has denied U.S. allegations that his government pursued nuclear weapons with the help of North Korea.

Hayden said a report from the unnamed foreign partner first identified the facility as a reactor similar to one in North Korea, although U.S. intelligence had identified it as suspicious.

"When pipes for a massive cooling system were laid out to the Euphrates River in the spring of 2007, there would have been little doubt this was a nuclear reactor," Hayden said.

"We would have known it was North Korean, too, given the quantity and variety of intelligence reports on nuclear ties between Pyongyang and Damascus."