Faced with that demand, senators have contemplated lifting the cap to around 100,000, with the ability to go as high as 150,000, aides and officials said. They spoke on condition of anonymity because negotiations were ongoing, and they stressed the numbers remained in flux and no final decisions had been made.

Such an increase would be a win for the tech industry, which has boosted its lobbying muscle in Washington in recent years. On a related issue, the legislation also is likely to allow permanent U.S. residency to unlimited numbers of people who get advanced degrees in science, technology or math from U.S. universities.

But the proposal to increase H-1B visas is focusing attention on problems with the current system.

Daniel Costa, immigration policy analyst at the Economic Policy Institute, a left-leaning think tank, said the top 10 companies with the most H-1B visas last year were all firms that bring workers here to work at lower cost than Americans would, then send them back home. Many are technology companies based in India.

"There need to be some major reforms before expansion happens," Costa said.

Senate negotiators have discussed fees and other penalties for companies that use large numbers of H-1B workers, including requiring those with more than 30 percent of their workforce made up of H-1B workers to pay higher wages than others, and those with more than 50 percent of H-1B workers to pay higher wages still. There would potentially be a prohibition against a company hiring more than 75 percent of its workers on H-1B visas. No such limit exists in current law.

But Durbin has been pushing to block companies from hiring any more than 50 percent of their workers on H-1B visas, aides and officials said. More problematically for U.S. firms, he also is pushing for higher wages, which industry officials contend could result in H-1B workers getting paid more than their American counterparts. And he's sought to push companies to make greater efforts to hire American workers first.

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