Pakistan and Russia are two nations that could be potential sources of leaking nuclear weapons technology or fissile materials to terrorists, according to a new report by the Congressional Research Service (CRS) on nuclear terrorism.
"The fear regarding Pakistan is that some members of the armed forces might covertly give a weapon to terrorists or that, if President Musharraf were overthrown, an Islamic fundamentalist government or a state of chaos in Pakistan might enable terrorists to obtain a weapon," the report said.
"Terrorists or rogue states might acquire a nuclear weapon in several ways. The nations of greatest concern as potential sources of weapons or fissile materials are widely thought to be Russia and Pakistan," it added.
Pakistan, a close ally of the US in the war against terrorism, has often been described by South Asia experts as a "potential source" of radicalism, proliferation, terrorism and even nuclear war.
The report said that although it would be difficult for the terrorists to launch a nuclear attack on any American city, such an attack is plausible and would have catastrophic consequences - in one scenario killing over a half a million people and causing damage of over $1 trillion.
Russia, the report noted, has many tactical nuclear weapons as well as much highly enriched uranium (HEU) and weapons grade plutonium, which do not have adequate safeguards.
Many experts believe that technically-savvy terrorists could fabricate a nuclear bomb from HEU. Terrorists could also obtain HEU from the more than 130 research reactors worldwide, most of which remain unprotected.
"If terrorists acquired a nuclear weapon, they could use many means in an attempt to bring it into the United States. This nation has many thousands of miles of land and sea borders, as well as several hundred ports of entry."