Washington —- Microsoft Corp. Chairman Bill Gates urged lawmakers on Wednesday to loosen America's immigration policies, lest the country "throw away" its global competitiveness.

Gates has long maintained that the government should issue more green cards and raise its annual 65,000 cap on the H-1B visa, a maximum six-year work permit that allows tech companies to bring in skilled foreign workers they say the United States lacks.

When talented foreigners can't get the visa, Gates argued, American companies cannot find qualified American researchers and other workers to fill the positions, and the country's competitive edge erodes further.

"You ask, 'How do we compete with Asian countries?' " said Gates, who was invited to testify before the House Science and Technology Committee on its 50th anniversary. "The fact that their smartest people want to come here is a huge advantage for us. But we're throwing that away."

Gates mostly received a warm reception in what likely was his final congressional appearance as Microsoft chairman (he steps down in July), but his testimony reflected the contentious nature of the visa debate.

Feet tapping, Gates spoke placidly until challenged by lawmakers who contend that an influx of foreign workers forces qualified Americans out of jobs, and the greater supply of workers is depressing American wages.

"There are plenty of [Americans] out there to hire," said Rep. Dana Rohrabacher (R-Calif.), quoting a BusinessWeek article. "But people want to have top-quality people from India and China and elsewhere, and they're willing to let these 150,000 American computer programmers just go unemployed."

Congress is bracing for a clash over the H-1B quota. Senators such Chuck Grassley (R-Iowa) and Richard Durbin (D-Ill.) promised a crackdown on "unscrupulous employers who deprive Americans of high-skill jobs," introducing a bill in 2007 that mandates employers to first hire American workers before looking overseas and prohibits companies from hiring H-1B employees if they have more than 50 employees and half are already on the work visa.

The tech sector, with Gates as its champion, is pushing for the yearly cap to be raised to 115,000.

The cap was reduced from 195,000 in 1995 to the current 65,000. In April 2007, a scramble for fiscal year 2008 petitions forced the immigration service to close the application window after several hours, sparking protests in the Indian media.

Wariness over bringing in foreign talent reflects a number of concerns. Rep. Phil Gingrey (R-Ga.) expressed unease that "Asian and Indian names" increasingly dominate newspaper lists of top SAT scores in his Marietta district, and asked Gates whether "youngsters who look like me" —- the congressman is white —- might find the influx of skilled foreign workers to be a deterrent in pursuing careers in technology and engineering.

"Our youngsters are competing with these students even if we turn them away from this country," Gates responded. "Computer science is not a game played only in the United States. At the end of the day, you're going to compete with the best in the world."

But Gates also had the support of several lawmakers who agree with raising the visa cap, including Rep. Michael McCaul (R-Texas), who represents Austin and its tech-heavy industries.

"I see the students at the University of Texas building computer chips," McCaul said. "Then I find out that after we invest and train them, we lose them and they go back to where they come from, usually China or Asia, and work for our competitors. That seems to be a failed policy in my view."

Gates said that for every H-1B job offered, four American jobs are created around it to meet administrative and support needs. He disputed that Americans are being squeezed out, because a dwindling number of college graduates in computer science or engineering fields, plus the visa limit, means specialized positions at companies "are going begging," he said.

Gates urgently called for better science and technology education and more federal funding for teachers in those subjects.