WASHINGTON - Republicans and Democrats were nearing a deal yesterday on an immigration overhaul that would give millions of illegal immigrants a chance at legal status but strictly limit future arrivals from staying in the country.

Senators and White House officials negotiating into the evening said an elusive compromise was in sight. But with details changing rapidly, it was unclear whether the talks would result in a breakthrough or a meltdown.

"Eighty-twenty!" said an upbeat Sen. Lindsey Graham (R., S.C.), one of the key participants in the talks, giving strong odds of a deal that he said could be announced as early as today.

In a sign for a potential deal, Senate Majority Leader Harry Reid (D., Nev.) postponed until Monday a vote that had been scheduled for today on bringing up an immigration measure that passed the Senate last year.

That bill had the support of most Democrats but was opposed by a majority of Republicans, who had promised to block it. The vote, designed to pressure negotiators into reaching a new deal, was shaping up as a highly partisan start to the already intense debate over immigration.

Delaying it gave the weeks-long set of closed-door bipartisan talks - slated to continue early today - more time.

Negotiators led by Sens. Jon Kyl (R., Ariz.) and Edward M. Kennedy (D., Mass.) scrambled to piece together a compromise that could command broad support, melding the GOP's preference for get-tough enforcement measures and limits on future immigration with Democrats' desire for a more welcoming approach.

The proposed agreement would allow illegal immigrants to come forward and obtain a probationary "Z visa" and, after paying fees and fines of up to $5,000 and returning to their home countries, ultimately try for permanent residency, which could take eight to 13 years. The process could not begin until border-security improvements and a high-tech worker ID program were completed.

A new temporary-guest-worker program also would have to wait until those so-called triggers had been activated. And all but the highest-skilled temporary workers would have to return home after work stints of two or three years.

Only 10,000 green cards a year would be available for guest workers, to be awarded on a so-called points system that favors higher-skilled and better-educated immigrants.

In perhaps its most contentious change, the proposed plan would radically shift the entire immigration system from one heavily weighted toward family ties toward one with preferences for those with advanced degrees and sophisticated skills. U.S. citizens would see their ability to bring foreign-born parents to this country limited.