The technology industry and organized labor are locked in a fight that threatens to complicate the U.S. Senate's immigration bill.

At the heart of the debate is whether there is a shortage of Americans with the math and science skills needed for work at technology firms like Facebook Inc, Google Inc and Microsoft Corp.

Labor is brandishing research that says the scarcity of workers is a myth while the tech industry is pointing to other studies that say the shortage is very real and is a threat to U.S. competitiveness.

In behind-the-scenes maneuvering that has created a quandary for Senate supporters of a broad immigration bill, lobbyists say Silicon Valley is pulling out all the stops to fight restrictions on a foreign-worker visa program known as H-1B that is aimed at making sure Americans get the first crack at any job openings.

Talks are expected to be ongoing this weekend to try to resolve the dispute over the high-skilled visa program that has proved to be a stumbling block for the Senate Judiciary Committee, which aims to vote on the immigration legislation by the end of the month.

If a deal can't be reached, it could alienate tech companies that have told lawmakers they might reconsider their support for the bill. It could also cost the vote of a key Republican senator, Orrin Hatch of Utah, who is on the fence about the legislation.

LABOR SAYS PLENTY OF U.S. WORKERS

The immigration bill, President Barack Obama's top domestic legislative priority, would create a path to citizenship for some 11 million undocumented immigrants, step up border enforcement and nearly triple the number of visas for high-skilled foreign workers. The legislation, drafted by a bipartisan group of eight senators, would also create new guest worker programs for low-skilled jobs such as waiters, hotel workers and construction workers.

The AFL-CIO has accused the tech industry, which has put its huge lobbying muscle into the fight, of becoming "greedy." The companies have already had a great deal of influence on the legislation and are now "trying to get more and more and more," said Andrea Zuniga DiBitetto, legislative representative with the AFL-CIO.

A study that labor and its allies have been touting has become a flashpoint for its dispute with Silicon Valley. The report from the liberal Economic Policy Institute (EPI) think tank, says the United States has "more than a sufficient supply" of workers with education in science, technology, engineering and math, known as STEM. It says that for every two students graduating from U.S. colleges with such degrees, only one has been getting hired in science or technology fields. (EPI study:)

The EPI study also says there has been wage stagnation in these fields for years, which it says means workers lack the power to bid up salaries because there aren't enough job openings.

"If there's a shortage, why don't you increase wages?" said Hal Salzman, one of the authors of the EPI study.

In a scathing criticism of the EPI study, Robert Hoffman of the Information Technology Industry Council (ITIC) - which represents companies such as Apple Inc, Microsoft and Google - pointed to 83,000 job openings that were listed on Dice.com, which posts tech job listings. He also cited data at the government's Bureau of Labor Statistics that he said shows a huge demand for computer science majors that is not met by the number of people graduating in the field.

"This would suggest, for EPI at least, that U.S. employers are engaged in a massive conspiracy to advertise for U.S. STEM jobs that do not exist," Hoffman wrote in a blog post last month on the ITIC web site. "That's quite a conspiracy. I wonder if EPI thinks we faked the moon landing."

TECH FIRMS SAYS SHORTAGE OF WORKERS

Hoffman pointed to a separate study put out this month by the

Hatch is championing the cause of the tech industry, which wants changes in a provision requiring that companies advertise jobs on a government-run website and offer them first to qualified Americans. Tech companies want most firms to only be required to make "good faith" efforts to hire Americans.

The AFL-CIO's most powerful ally in the fight over skilled-worker visas is Senator Richard Durbin, an Illinois Democrat who sits on both the Judiciary Committee and is one of the eight senators who wrote the immigration bill.

In a sign that he is at least open to talking about a way to satisfy the tech industry, Durbin, when asked if there was a deal yet on the dispute, said on Thursday morning, "We're working on it."