The material, used as a power source, would primarily be used for secret national security missions, according to people involved in the project who declined to give further details, the New York Times said.

In the past nuclear batteries made from plutonium 238 were used to power satellites, planetary probes and spy devices, it said.

"Plutonium 238 is hundreds of times more radioactive than the kind of plutonium used in nuclear arms, plutonium 239," the daily said.

The plan, to be submitted to Congress some time in 2006, calls for the manufacture of 150 kilograms (330 pounds) over 30 years, starting in 2012. The program would cost 1.5 billion dollars and generate more than 50,000 drums of hazardous and radioactive waste, according to the Times.

Production would take place at the sprawling Idaho National Laboratory, raising the ire of environmentalists because of its proximity to prized wilderness areas such as Grand Teton National Park and Yellowstone National Park.

The United States last manufactured plutonium 238 during the Cold War in the 1980s, and currently relies on Russian imports, which cannot be used for military purposes, and on its own stockpiles, which are fast depleting.

Plutonium is an artifically produced element created by bombarding uranium-238 with deuterons. Two of plutonium's several isotopes are used outside of basic research -- plutonium 239, which forms the core of nuclear wearheads and some nuclear reactors, and plutonoum 238, which has been used primarily on space probes too distant from the sun to use solar power.

The accidental destruction of a satellite powered by plutonium 238 in 1964 spread radioactivity around the globe, the Times said.

Experts say newer nuclear batteries are far safer and the risk of human exposure is "extraordinarily low," according to the daily