The six-month inquiry singles out Pakistan as one of the likeliest sources of such an attack

A congressional investigation into weapons of mass destruction today offered a chilling prediction of terrorists mounting an attack using biological or nuclear weapons within the next five years.

The six-month inquiry singles out Pakistan as one of the likeliest sources of such an attack. The target could be the US or some other part of the world.

The report, by the bipartisan Commission on the Prevention of Weapons of Mass Destruction, concludes that "unless the world community acts decisively and with great urgency, it is more likely than not that a weapon of mass destruction will be used in a terrorist attack somewhere in the world by the end of 2013".

It adds that "terrorists are more likely to be able to obtain and use a biological weapon than a nuclear weapon".

President George Bush welcomed the report, saying the threat posed was the greatest facing the US and was "dangerously real". He said that after the 9/11 attacks, he had put in place policies tackling the threat and he was leaving a good foundation for his successor.

The incoming Barack Obama administration, which is to make proliferation of weapons of mass destruction a priority, was briefed on Capitol Hill today about the findings in the 132-page report.

The commission, which was led by the former Democratic senator Bob Graham and by former Democratic senator Jim Talent, was given six months to complete the report. It follows on from the work of the commission that investigated the 9/11 attack.

Graham told reporters at the press conference that a biological or nuclear attack within the next five years was not inevitable and the commission's reports included a series of recommendations, that if implemented, could diminish the threat. Recommendations include creation of a White House post focusing on proliferation and more emphasis on diplomatic efforts.

The team's remit ranged from lack of security at biological labs in the US to the safety of nuclear stockpiles in Russia. It conducted 250 interviews with scientists, analysts, intelligence agencies and the military.

The report concludes the risk from biological or nuclear weapons is higher than sceptical foreign policy and defence analysts have suggested. Those analysts had pointed to the complexity of transporting biological or nuclear weapons and the limitations of a nuclear "dirty" bomb, whose radius of damage is minimal compared with missile-delivered warheads.

The report disagrees, saying: "No mission could be timelier. The simple reality is that the risks that confront us today are evolving faster than our multilayered responses. Many thousands of dedicated people across all agencies of our government are working hard to protect this country, and their efforts have had a positive impact. But the terrorists have been active, too and in our judgment America's margin of safety is shrinking, not growing."

It adds that much dangerous biological and nuclear material around the globe is "poorly secured and thus vulnerable to theft by those who would put these materials to harmful use, or would sell them on the black market to potential terrorists."

As well as the threat from stateless militant groups, the commission expresses concern about the danger posed by proliferation of nuclear weapons to states such as Iran, saying the Obama administration must stop it from acquiring a nuclear weapons capability.

It points to Pakistan, both at the state level and among stateless groups, as one of the areas of most concern. "Were one to map terrorism and weapons of mass destruction today, all roads would intersect in Pakistan," the report says.

Talent told the press conference in Washington today: "It is the epicentre of a lot of these dangers." He said the report had been drawn up before the Mumbai attacks.

The commission recommends that Pakistan be top priority for the Obama administration in terms of terrorism and proliferation. Proposals include eliminating terrorist safe havens through military, economic, and diplomatic means, securing nuclear and biological materials in Pakistan, countering and defeating extremist ideology, and constraining a nascent nuclear arms race in Asia.

Other recommendations include strengthening the non-proliferation treaty and other international safeguards, creating a US national security force appropriate to the 21st century and developing a more coherent strategy for countering ideologies that leads to terrorism.

At home, the commission was disturbed at the apparent lack of security at laboratories dealing with dangerous biological materials. Government investigators, sent to check on the vulnerability of such sites were able gain access to the outside of these buildings and observe work inside.

It was lucky that they were from the government and not al-Qaida operatives as these were precisely the lethal trove that the terrorists have been seeking for years, the report says.

The government investigators watched a pedestrian simply stroll into one of the buildings through an unguarded loading bay.

The commission recommended tighter oversight of the 400 research facilities and 15,000 staff engaged in such work. Another recommendation is the establishment of an anthrax preparedness strategy.