The United States can expect a terrorist attack using nuclear or biological weapons within the next five years, a US study leaked today said.

The United States can expect a terrorist attack using nuclear or biological weapons within the next five years, a US study leaked today said.

The report by a bipartisan commission, which will be published officially tomorrow, said the margin of safety in America was "shrinking, not growing" and urged the US to "move with a sense of urgency", saying that "time is not our ally".

It also said the potential nexus of terrorism, nuclear and biological weapons was especially acute in Pakistan.

The report of the Commission on the Prevention of WMD Proliferation and Terrorism, led by former senators Bob Graham of Florida and Jim Talent of Missouri, also suggested the incoming Obama administration should bolster efforts to counter and prepare for germ warfare by terrorists.

"Our margin of safety is shrinking, not growing," it said, according to the Associated Press which obtained a copy.

The commission said biological weapons were more likely to be obtained and used before nuclear or radioactive weapons because nuclear facilities were more carefully guarded.

It said civilian laboratories with potentially dangerous pathogens abound, and could easily be compromised.

"The biological threat is greater than the nuclear; the acquisition of deadly pathogens, and their weaponisation and dissemination in aerosol form, would entail fewer technical hurdles than the theft or production of weapons-grade uranium or plutonium and its assembly into an improvised nuclear device," the report said.

It acknowledged that terrorist groups still lack the scientific and technical ability to make weapons out of pathogens or nuclear bombs, but said the gap could easily be overcome if terrorists found scientists willing to share or sell their know-how.

"The United States should be less concerned that terrorists will become biologists and far more concerned that biologists will become terrorists," the report said.

The commission also encouraged the new White House to appoint one official on the National Security Council to exclusively co-ordinate US intelligence and foreign policy on combating the spread of nuclear and biological weapons.

Study chairman Mr Graham said anthrax remained the most likely biological weapon, but that contagious diseases - like the flu strain that killed 40 million at the beginning of the 20th century - were looming threats.

That virus has been recreated in scientific labs, and there remains no inoculation to protect against it if is stolen and released.

Mr Graham said the threat of a terrorist attack using nuclear or biological weapons was growing "not because we have not done positive things but because adversaries are moving at an even faster pace to increase their access" to those materials.

"We think time is not our ally. The (United States) needs to move with a sense of urgency," he said.

Referring to last week's terror attacks by a small group of gunmen in Mumbai, he went on: "If those people had had access to a biological or nuclear weapon they would have multiplied by orders of magnitude the deaths they could have inflicted."

The report also found that al-Qaida remains the only terrorist group judged to be actively intent on conducting a nuclear attack against the US.

It is not yet capable of building such a weapon and has yet to obtain one, but that could change if a nuclear weapons engineer or scientist were recruited to al-Qaida's cause, the report warned.

It added: "Were one to map terrorism and weapons of mass destruction today, all roads would intersect in Pakistan."

Commission members were forced to cancel their trip to Pakistan earlier this year when the Islamabad Marriott Hotel, where they were due to stay, was blown up by terrorist bombs just hours before they were set to check in.