WASHINGTON (REUTERS) - Eager to secure more visas for skilled foreign workers, tech companies have stepped up their lobbying this week in support of a comprehensive US immigration reform bill.

Human resources executives from Adobe, Broadcom, Intel, Motorola Solutions and other corporations met with dozens of lawmakers and senior advisers on Wednesday from the congressional committees in charge of immigration laws.

They also spoke to a wide array of Democratic and Republican senators including some on-the-fence Republicans, such as Mark Kirk of Illinois and Rob Portman of Ohio, and some who have voiced opposition, including Mike Lee of Utah.

Lawmakers who favour the bill "have been urging us to work with them to make sure that the bill gets passed with the highest number of votes possible", said Robert Hoffman, senior vice president with the Information Technology Industry Council trade group.

The effort comes as the US Senate is working on immigration reform legislation. If enacted, the legislation would give 11 million illegal immigrants a chance to become citizens, use billions of US dollars in taxpayer funds to increase security at the US-Mexico border and establish a new work visa for foreign labourers.

The bill also boosts the number of visas available for highly skilled foreigners, which will benefit those with expertise in the so-called STEM fields of science, technology, engineering and math. The tech industry says such a step is badly needed.

"Even through the depth of the great recession, we struggled to fill jobs," said Ardine Williams, Intel's vice president for human resources, before making her case for the bill to lawmakers on Wednesday.

Earlier this week, another set of executives from Microsoft, Texas Instruments and other big tech firms roamed the halls of Capitol Hill trying to convince lawmakers to pass a comprehensive immigration bill.

Silicon Valley and other business groups were initially upset with a host of high-skill hiring provisions in the original bill drafted by a bipartisan "Group of Eight" senators, including Democrat Charles Schumer.

While the Senate Judiciary Committee was working on the bill in May, business groups threatened to withdraw their support if senators did not loosen requirements that would have required them to recruit Americans before foreigners.

Their demands pit the business community against organised labor, which had fought to keep the strict protections for US workers in the bill. But the lack of support from businesses would have represented a setback for the supporters of immigration reform and the Group of Eight.

With help from Republican Senator Orrin Hatch and Schumer, industry succeeded in having the bill changed to make it easier to hire foreign workers. Labour groups, which are lobbying Congress to pass an immigration bill that includes a path to citizenship for the undocumented foreigners, are hoping additional worker protections will be included in the final legislation.

Under the bill, the number of H-1B high-skill work visas would increase to as many as 180,000 a year from the current base limit of 65,000. As well, foreigners with a master's or doctorate degree from a US university and a job offer would be eligible for permanent residency, or green card, and not be subject to the yearly green-card cap.

Mr Schumer told the tech industry that if it got most of what it wanted, it would have to do more than issue press releases merely praising the Senate's efforts, industry sources said. The sources said they were told they would have to support the entire bill enthusiastically.

Tech lobbyists are now carefully wording their support for the entire bill without outright endorsing the centerpiece of the legislation - citizenship for illegal immigrants.

Compete America, which represents many companies in Silicon Valley and other influential business groups like the US Chamber of Commerce, has met with about 300 of the 435 lawmaker offices that make up the House of Representatives.

At least 60 votes will be required to pass the legislation in the Senate. Mr Schumer and other authors of the bill are trying to get more Republican votes in order to pressure the Republican-controlled House into acting.

Democrats control 54 of the 100 seats in the Senate. It is unclear whether every Democrat will vote in favor of the legislation and if the four Republicans who helped craft the original bill will back the final product.