Washington - The chances that terrorists will use a nuclear or biological weapon to carry out an attack has grown increasingly likely and could happen in the next five years, according to a US congressional produced report released Tuesday.

The United States must move quickly to work with other countries to increase security and strengthen international organizations to prevent an attack from taking place, the report said.

Congress chartered the Commission on the Prevention of Weapons of Mass Destruction Proliferation and Terrorism to evaluate the risk and provide president-elect Barack Obama with an assessment.

"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," the report said.

The United States should call for an international conference to help set higher security standards at biological and nuclear facilities and toughen the nuclear Non-Proliferation Treaty (NPT). The International Atomic Energy Agency (IAEA), the UN body that monitors nations' nuclear activities and enforces the NPT should also be strengthened.

"No mission could be timelier," the report said. "The simple reality is that the risks that confront us today are evolving faster than our multilayered responses."

The report singled out Pakistan as among countries that poses a larger risk because of the widespread presence of terrorist organizations, political instability and it stockpile of nuclear weapons.

Although a biological attacks is more likely than nuclear, the report said the threat of a nuclear attack is rapidly increasing.