IBM on Wednesday claimed it has built the world's fastest supercomputer, wresting the title from Japanese company NEC.

The new supercomputer, dubbed Blue Gene/L, claimed to sustain speeds of 36 teraflops (36 trillion calculatons per second), surpassing Japanese 'Earth Simulator' which has a speed of 35.86 teraflops.

There are 500 supercomputers in the world and IBM's new system would mark the first time in three years that the world's fastest supercomputer is located in the United States.

"A lot of policymakers in Washington have worried about the (Japanese) Earth Simulator as an example of the US computer industry falling behind," said Dave Turek, an IBM vice president who oversees supercomputing efforts.

"But, by far, the great majority of systems on the top 500 supercomputer list have come from US-led companies."

The Japanese company had designed the Earth Simulator to simulate earthquakes.

The prototype of the Blue Gene/L system, located in Rochester, Minnesota, has 16,250 processors and takes up eight racks of space.

IBM plans to build an even larger and faster version of the Blue Gene computer for the Lawrence Liermore National Laboratory in California, a project scheduled for completion in May 2005.

Lawrence Livermore lab, built to design nuclear weapons and work on other defence projects, has a 'never-ending appetite' for computational power to help model molecular and nuclear behaviour, Turek said.