WASHINGTON (REUTERS) - Senate negotiators have reached a tentative deal with tech companies to ease restrictions on hiring foreigners for high-skilled jobs as part of a sweeping immigration bill, congressional and industry sources said on Tuesday.

Judiciary Committee members have been in negotiations with the companies and the AFL-CIO union over whether to lift constraints on H-1B visas allowing American companies to hire highly skilled foreign workers.

Under the deal struck between Democratic Senator Charles Schumer of New York and Republican Senator Orrin Hatch of Utah, the Senate would back a looser formula for determining the annual number of H-1B visas issued.

But no increase could occur if the US unemployment rate in the particular profession was 4.5 per cent or higher, or if the jobless rate in that sector was greater than in the previous 12-month period.

Schumer also accepted one of Hatch's most contentious proposals, strongly opposed by the AFL-CIO, that only requires "H-1B dependent" companies to make an effort to hire Americans for the jobs first.

The immigration bill currently requires all companies that hire H-1B employees, not just those that are defined as dependent on the high-skill visas, to initially recruit US workers.

Hatch has said he would seek additional changes during debate in the full Senate. The bill is now before the Judiciary Committee.

Those are thought to have to do with whether illegal immigrants who would be granted legal status could qualify for government programs such as Social Security and tax credits for children and families with low incomes.

The tentative deal needs approval from the Judiciary Committee, and the entire immigration bill needs to pass the Senate and House of Representatives before President Barack Obama can sign it into law.