Report: Iranian defector tipped Syrian nuclear plans

"The biggest surprise, however, was his assertion that Iran was financing a secret nuclear project of Syria and North Korea," he said. "No one in the American intelligence scene had heard anything of it. And the Israelis who were immediately informed also were completely unaware."

In Washington, however, a US counterproliferation official denied that Iran funded the Syrian site.

"There is strong reason to believe that only two countries were involved in building the Syrian covert nuclear reactor at Al Kibar - Syria and North Korea," said the official, who spoke on condition of anonymity.

Ruehle, who did not identify the sources of his information, regularly publishes and comments on security and nuclear proliferation in different European newspapers and broadcasts, and he has held prominent roles in German and NATO institutions.

He said US and Israeli intelligence had detected North Korean ship deliveries of construction supplies to Syria that started in 2002, and American satellites spotted the construction as early as 2003.

But they regarded the work as nothing unusual, in part because the Syrians had banned radio and telephones from the site and handled communications solely by messengers - "medieval but effective," Ruehle said.

Intensive investigation followed by US and Israeli intelligence services until Israel sent a 12-man commando unit in two helicopters to the site in August 2007 to take photographs and soil samples, he said.

"The analysis was conclusive that it was a North Korean-type reactor," a gas graphite model, Ruehle said.

Israel estimates that Iran had paid North Korea between $1 billion and $2 billion for the project, Ruehle said.

Israel has refused from the beginning to comment on, confirm or deny the strike, but after a delay of several months Washington presented intelligence purporting to show the target was a reactor being built with North Korean help.

Iranian officials were not available for comment yesterday. In general, Iran has been silent about the Syrian facility bombed by Israel.

Syrian officials could not be reached for comment. But Syria has denied the facility was a nuclear plant, saying it was an unused military building.

The International Atomic Energy Agency earlier this year said UN inspectors had found processed uranium traces in samples taken from the site.