A bipartisan group of leading senators has reached agreement on the principles of sweeping legislation to rewrite the immigration laws of the United States.

The deal, which was scheduled to be announced on Monday afternoon, covers border security, guest workers and employer verification, as well as a path to citizenship for the 11 million illegal immigrants already in the country.

Although thorny details remain to be negotiated and success is far from certain, the development heralds the start of what could be the most significant effort in years toward overhauling the nation's inefficient patchwork of immigration laws.

US President Barack Obama also is committed to enacting comprehensive immigration legislation and will travel to Nevada on Tuesday to lay out his vision, which was expected to overlap in important ways with the Senate effort.

The eight senators expected to endorse the new principles on Monday are Democrats Charles Schumer of New York, Dick Durbin of Illinois, Robert Menendez of New Jersey and Michael Bennet of Colorado; and Republicans John McCain of Arizona, Lindsey Graham of South Carolina, Marco Rubio of Florida and Jeff Flake of Arizona.

Several of these lawmakers have worked for years on the issue. McCain collaborated with the late Democratic senator Edward Kennedy on comprehensive immigration legislation pushed by then-president George W. Bush in 2007, only to see it collapse in the Senate when it couldn't get enough GOP support.

Now, with some Republicans chastened by the November elections, which demonstrated the importance of Latino voters and their increasing commitment to Democrats, some in the Republican Party say this time will be different.

"What's changed, honestly, is that there is a new, I think, appreciation on both sides of the aisle - including maybe more importantly on the Republican side of the aisle - that we have to enact a comprehensive immigration reform bill,'" McCain said on Sunday on ABC's This Week.

"I think the time is right," McCain said.

The group claims a notable newcomer in Rubio, a potential 2016 presidential candidate whose conservative bona fides may help smooth the way for support among conservatives wary of anything that smacks of amnesty. In an opinion piece published on Sunday in the Las Vegas Review-Journal, Rubio wrote that the existing system amounts to "de facto amnesty," and he called for "commonsense reform".

Under the group's proposal, undocumented immigrants would be allowed to register with the government, pay a fine, and then be given probationary legal status allowing them to work.

Ultimately, they would have to "go to the end of the line" and apply for permanent status.

AP-Reuters