The fastest computer in the world today, the Blue Gene/L supercomputer at the Lawrence Livermore National Lab.

SAN FRANCISCO, Aug. 18 - A global race is under way to reach the next milestone in supercomputer performance, many times the speed of today's most powerful machines.

And beyond the customary rivalry in the field between the United States and Japan, there is a new entrant - China - eager to showcase its arrival as an economic powerhouse.

The new supercomputers will not be in use until the end of the decade at the earliest, but they are increasingly being viewed as crucial investments for progress in science, advanced technologies and national security.

Once the exclusive territory of nuclear weapons designers and code breakers, ultrafast computers are increasingly being used in everyday product design. Procter & Gamble used a supercomputer to study the airflow over its Pringles potato chips to help stop them from fluttering off the company's assembly lines.

Today, driven by advances in so-called parallel computing - with software making it possible to lash together arrays of tens or even hundreds of thousands of processor chips - the speed of future supercomputers is limited only by cost, adequate electricity and the ability to cool the systems, which now sprawl over thousands of square feet.

China now has 19 supercomputers ranked among the 500 fastest machines, and recent reports in Chinese newspapers stressed the importance of developing high-performance computing technology not dependent on the United States.

"It's becoming an issue of national pride," said Steve Wallach, a supercomputer designer who is a vice president at Chiaro Networks, a technology provider for high-performance computing. "That's where the Japanese are coming from, and now the Chinese want to be viewed as a Tier 1 country in every respect."

Indeed, in recent weeks there have been reports that both the Japanese and Chinese are planning new investments in breaking the petaflop computing barrier. A petaflop is a measure of computing performance that describes the ability to perform 1,000 trillion mathematical operations a second, roughly eight times the speed of today's fastest computer.

"Everyone appears to be in the race for a petaflop," said Jack Dongarra, a computer scientist at the University of Tennessee who maintains a list of the world's fastest computers.

Currently the world's fastest computer is a machine installed at Lawrence Livermore National Laboratory late last year - and still growing - that has reached more than 136 trillion operations a second, or 100,000 times the speed of a fast desktop personal computer. I.B.M. built the machine, Blue Gene/L, and plans to double its speed before the end of the year.

Only small amounts of research funds have been spent so far on designing a petaflop supercomputer, an accomplishment that Japanese and American experts believe will cost nearly $1 billion for each machine to achieve. But 10 companies have indicated that they are doing preliminary work, Mr. Dongarra said.

In the United States, Cray, I.B.M. and Sun Microsystems have begun work toward reaching a petaflop by the end of the decade, supported by a development project financed by the Pentagon.

The project, the High Productivity Computer Systems program of the Defense Advanced Research Projects Agency, or Darpa, was begun in 2003 with about $150 million as one of a series of American responses to the emergence of a Japanese supercomputer - the Earth Simulator, intended for climate research - as the world's fastest in 2002, displacing the United States for the first time.

With significant financial support from the government, I.B.M., Cray and Silicon Graphics all built new massively parallel supercomputers, enabling the United States to recapture world leadership in November 2004. In the most recent ranking of the world's 500 fastest computers, released in June, the United States holds the top three positions. The Earth Simulator has fallen to fourth place, with about a quarter the computing speed of the new leader.

Some executives say they believe the United States is well positioned to remain dominant in computing technologies. "There is a lot less angst in the U.S. than there was previously," said David Turek, vice president for high-performance computing at I.B.M. "We're not asleep at the switch."

But the fastest American machines are used primarily for military applications at the nation's weapons laboratories. Many scientists and technology executives in the United States are concerned about losing out in crucial markets like oil and gas exploration, automobile design and manufacturing unless they, too, have access to the fastest supercomputers. They contend that a public-private partnership is needed to develop supercomputers whose applications are not limited to the military.

Not all supercomputer experts are convinced that having the world's fastest computer is essential to American competitiveness.

"I.B.M. and Cray are doing a good job of ensuring that the U.S. remains competitive in the high-performance computing market," said C. Gordon Bell, a Microsoft researcher and a former supercomputer designer. Because the very largest computers are so difficult to program, their impact in the short term is relatively limited, he added.