WASHINGTON, Nov 24: The US Central Intelligence Agency has now officially accused Dr A. Q. Khan of providing Iran with technology and equipment for making a nuclear bomb, indicating a major shift in US approach to the dispute.

In the past, all such allegations were made in leaks to the US media, always attributed to unnamed American officials. The CIA report comes amid demands by US lawmakers and non-proliferation activists to bring Dr Khan to the United States for interrogation or at least to send American experts to interview the disgraced Pakistani scientist living under house arrest since February.

The unclassified version of the report sent to the US Congress says that "the A. Q. Khan network provided Iran with designs for Pakistan's older centrifuges, as well as designs for more advanced and efficient models, and components."

The report posted on the CIA website this week, however, does not say explicitly whether the Khan network sold Iran complete plans for building a warhead. But congressional sources told reporters that the classified version sent to Congress does make this allegation.

In the past, US officials had reported that the network supplied complete bomb-making plans to Libya and perhaps North Korea. But the CIA now believes that the bomb-making designs the Khan network gave to Iran in the 1990's were more significant than the US government had previously disclosed, the report said.

Also on Wednesday, the New York Times published excerpts from a speech former CIA director George J. Tenet gave to a private, closed-door gathering. In that speech, Mr Tenet describes Dr Khan as being "at least as dangerous as Osama bin Laden" because of his role in providing nuclear technology to other countries.

Until now, in discussing Iran's nuclear programme, American officials have referred publicly only to the Khan network's role in supplying designs for older Pakistani centrifuges used to enrich uranium and known as P-1 and P-2.

Although American officials had suspected that the Khan network provided Iran with a warhead design as well, they never made this allegation publicly. The CIA report is the first to assert that the designs provided to Iran also included those for weapons "components."

The report to Congress is an annual update, required by law, on countries struggling to acquire illicit weapons technology. The posting of the unclassified version on the agency's website comes two days before the International Atomic Energy Agency is scheduled to review the status of Iran's weapons programme in Vienna.

The "report to Congress on the Acquisition of Technology Relating to Weapons of Mass Destruction and Advanced Conventional Munitions" is the first to be issued by the agency since November. It focuses on the period from July to December 2003, but also discusses broader trends.

The report says the warhead design the Khan network provided to Libya was for an aging, crude Chinese model. Such a design would nevertheless provide Iran with important assistance in is its quest to develop nuclear weapons, a goal they say Tehran could reach in the next several years, the CIA says.

The NYT report, quotes Mr Tenet as saying that the CIA began to infiltrate Dr Khan's network in the late 1990's, long before the Sept 11, 2001 terrorist attacks in the United States. That operation led to the unravelling of the network's ties to Libya and the unmasking last year of Libya's illicit weapons programme.

Libya turned over the design to the United States early this year, and it is now being examined by US nuclear experts. The NYT says that American intelligence agencies are still pursuing questions about the extent of the role the Khan network played in providing assistance to North Korea, Iran and perhaps other customers.

A recent report by the IAEA noted "several common elements" between Iran's nuclear programme and Libya's, which is being dismantled. The unclassified version of the CIA report also expresses concerns that outside experts, including a Pakistani nuclear engineer, may have provided assistance to Al Qaeda as part of its quest to acquire nuclear weapons. "One of our highest concerns is Al Qaeda's stated readiness to attempt unconventional attacks against us," the report says.