Washington: UN investigators have identified a previously unknown complex in Syria that bolsters suspicions that the Syrian government worked with A Q Khan, the father of Pakistan's atomic bomb, to acquire technology that could be used to make nuclear arms.

The buildings in northwest Syria closely match the design of a uranium enrichment plant provided to Libya when Muammar Gaddafi was trying to build nuclear weapons under Khan's guidance, informed officials.

The UN's International Atomic Energy Agency also has obtained correspondence between Khan and a Syrian government official, Muhidin Issa, who proposed scientific cooperation and a visit to Khan's laboratories following Pakistan's successful nuclear test in 1998.

The complex, in the city of Al-Hasakah, now appears to be a cotton-spinning plant, and investigators have found no sign that it was ever used for nuclear production. But given that Israeli warplanes destroyed a suspected plutonium production reactor in Syria in 2007, the unlikely coincidence in design suggests that Syria may have been pursuing two routes to an atomic bomb: uranium as well as plutonium.

Details of the Syria-Khan connection were provided  by a senior diplomat with knowledge of IAEA investigations and a former UN investigator. Both spoke on condition of anonymity because of the sensitivity of the issue.

The Syrian government did not respond to a request for comment. It has repeatedly denied pursuing nuclear weapons but also has stymied an investigation into the site bombed by Israel. It has not responded to an IAEA request to visit the Al-Hasakah complex, the officials said.

The IAEA's examination of Syria's programmes has slowed as world powers focus on a popular uprising in the country and the violent crackdown by government of President Bashar Assad.

Syria never has been seen as being close to development of a nuclear bomb. There also is no indication that Damascus continues to work on a secret nuclear programme.

If the facility in Al-Hasakah was indeed intended for uranium production, those plans appear to have been abandoned and the path to a plutonium weapon ended with Israeli bombing.

But Mark Hibbs, an analyst at the nuclear policy programme at the Carnegie Endowment for International Peace, who has spoken to IAEA officials about the Al-Hasakah complex, said it is important to learn more details about the buildings.

"What is at stake here is the nuclear history of that facility," Hibbs said. "People want to know what did they intend to do there and Syria has provided no information."

Syria has reasons to seek a nuclear weapon. It has been in a Cold War for decades with Israel, a country believed to have a sizable nuclear arsenal.

"A nuclear weapon would give Syria at least a kind of parity with Israel and some status within the region," says Anthony Cordesman, a national security analyst at the Center for Strategic and International Studies.

For years, there has been speculation about ties between the Syrian government and Khan.

A hero to many in Pakistan for developing the country's nuclear bomb, Khan is considered the world's most prolific nuclear merchant. He supplied Iran with the basics of what is now an established uranium enrichment programme that has churned out enough material to make several nuclear weapons.

Libya also bought equipment and a warhead design from Khan for a secret nuclear programme that it renounced in 2003.

In 2004, Khan confessed on TV to selling nuclear technology to Iran, North Korea and Libya, but he has never spoken of Syria. Khan later said Pakistani authorities forced him to make the confession.