As the US government opened up visa applications Monday for highly skilled immigrants, debate flared anew on the tech sector's demands to be able to hire more foreign workers.

The US tech sector has long complained of a shortage of workers with specialized skills, but the debate is further complicated this year by fresh attention to a broader immigration law aimed at bringing millions of undocumented migrants out of the shadows.

In what has become an annual rite for the tech sector, the US government opened applications for 65,000 spots for highly skilled workers under the so-called H-1B visa program.

US Citizenship and Immigration Services said it expects to receive more requests than available visas by April 5, and if so will set up a lottery.

"It will be a frenzy, because the cap of 65,000 visas is nowhere near high enough to meet demand," said Robert Holleyman, head of BSA/The Software Alliance.

"If you didn't know better, you might think the H-1B petition-filing frenzy had something to do with April Fool's Day. But it's no joke."

Microsoft general counsel Brad Smith said the squeeze has led to "increased anxiety" at many companies since the visas for the next fiscal year are likely to be filled in the first week.

Smith said in a blog post that the situation highlights a shortage in "STEM talent" -- people with degrees in science, technology, engineering and mathematics.

"The American economy creates 120,000 new computer-related jobs annually that require a bachelor's degree, but we are currently producing about 51,000 graduates with a degree in computer science each year," he said.

"We have first-hand experience with the challenges. Currently, Microsoft has 3,400 high-paying, high-skilled job openings in core technology areas that we cannot fill."

But sentiment on the issue is far from universal. Some critics claim the visa program tamps down US wages, while others say the system is abused by companies that outsource jobs to countries like India.

According to the Institute of Electrical & Electronics Engineers, the top 10 users of H-1B visas in the past fiscal year were companies specializing in shipping American jobs offshore.

Vin O'Neill, a spokesman for the IEEE-USA, said there is a long history of companies using the H-1B visas for short-term jobs, only to later transfer those functions elsewhere, often to India's booming tech sector.

"If companies need workers, they should bring people in as legal permanent residents rather than (on) a semi-permanent basis," O'Neill said.

"As legal residents, the workers are able to quit and move around. Their spouses can work. There are a lot of advantages."

O'Neill said using H-1B visas depresses wages because the workers are at the mercy of the employer, unable to seek a new job unless they find a new sponsor.

Senator Chuck Grassley has introduced a measure that would tighten controls for the H-1B program.

"The program was never meant to replace qualified American workers, but it was instead intended as a means to fill gaps in highly specialized areas of employment," Grassley said in a statement.

Grassley's proposal would requires companies to make a good faith effort to hire Americans first, and would bar companies from outsourcing visa holders to other companies.

It is unclear how the broad immigration overhaul will fare in Congress, but many see a high-tech component in any reform package. Analysts say the momentum is positive now that Republicans are anxious to improve their image with Hispanic voters after last year's election loss.

Marshall Fitz, director of immigration policy at the Center for American Progress think tank, said he sees a "synergy" with the tech sector and backers of a more broad immigration bill.

"This is the best opportunity for the tech sector get their provisions addressed and I think they know that," Fitz said.