"We can no longer afford to delay reform," said Republican Sens. John McCain and Edward M. Kennedy in a statement that capped weeks of struggle to find common ground.
President Bush, eager to find some legislative accomplishment in the face of low poll numbers, stepped up his own pressure on Capitol Hill and it seems to be working CBS News White House correspondent Jim Axelrod reports.
The Senate is moving toward President Bush's position: don't just tighten borders, figure out what to do with the illegal immigrants already here.
Mr. Bush said he was pleased with the developments and urged the Senate to pass legislation by week's end.
But the emerging compromise drew fire from both ends of the political spectrum. Conservative Sen. John Cornyn, R-Texas, likened it to an amnesty bill that cleared Congress in 1986, while AFL-CIO President John Sweeney said it threatened to "drive millions of hardworking immigrants further into the shadows of American society, leaving them vulnerable to exploitation."
Still, after days of partisan, election-year rancor, an overnight breakthrough on the future of illegal immigrants propelled the Senate closer to passage of the most sweeping immigration legislation in two decades.
A senior White House aide tells CBS News the president plans to become much more forceful now on getting House Republicans to see it his way on guest workers, so the immigration bill may very well tell us a lot about President Bush's current political condition.
In an indication of the complicated political forces at work, officials of both parties disagreed about which side had blinked. But they agreed that a decision to reduce the number of future temporary workers allowed into the country had broken a deadlock that threatened as late as Wednesday night to scuttle efforts to pass a bill. The change will limit temporary work permits to 325,000 a year, down from 400,000 in earlier versions of the bill.
Senate Majority Leader Bill Frist, R-Tenn., characterized the developments as a "huge breakthrough." Senate Democratic leader Harry Reid of Nevada said he was optimistic about final passage, but cautioned, "We can't declare victory."
Sen. Arlen Specter, R-Pa., chairman of the Senate Judiciary Committee, said: "While it admittedly is not perfect, the choice we have to make is whether it is better than no bill, and the choice is decisive."
Officials described a complex series of provisions:
Separately, the legislation provides a new program for 1.5 million temporary agriculture industry workers over five years.
It also includes provisions for employers to verify the legal status of workers they hire, but it was not clear what sanctions, if any, would apply to violators.
Assuming the Senate irons out remaining details and gets this passed, an immigration bill is still a very long way from becoming law. That's because the bill passed in the House is dramatically different, CBS News correspondent Bob Fuss reports. It declares all illegal immigrants to be felons, seeks to punish anyone who helps them in any way and orders a huge fence built along the Mexican border. Finding common ground with a Senate bill to legalize most illegal immigrants won't be easy.
To secure the border, the bill calls for a virtual fence, as opposed to the literal barrier contained in House legislation, consisting of surveillance cameras, sensors and other monitoring equipment along the long, porous border with Mexico.
Conservatives unhappy with the deal voiced their concerns to Frist, while Democrats sought assurances that the agreement would not be undercut in any future compromise talks with the House. McCain told reporters that he and other members of the GOP were circulating a letter pledging to vote against any changes demanded by the House that "would destroy this very delicately crafted compromise."
The House has passed legislation limited to border security, but Speaker Dennis Hastert, R-Ill., and other leaders have signaled their willingness in recent days to broaden the bill in compromise talks with the House.
The comments sparked a furious counterattack from critics.
"I can just about guarantee you we're not going to get a majority of the House members (to agree) on amnesty to 10 million people," Rep. Tom Tancredo, R-Colo., said at a news conference. "I am disappointed that apparently Mr. Frist has caved in to the desires of Democrats, to Kennedy," he added.
Tancredo's remarks underscored the unpredictable political fallout from the issue as Republicans seek legislation to fortify the borders without offending the fast-growing Hispanic voting population. Bush has long argued that a guest worker program is an essential element of border security, but potential challengers for the 2008 GOP nomination have come at the issue from a variety of perspectives.
McCain and Kennedy have worked hard to find common ground, and Sen. Sam Brownback, R-Kan., supported a bipartisan measure that emerged from the Senate Judiciary Committee.
Frist, a potential presidential candidate in 2008, sought to establish more conservative credentials when he initially backed a bill limited to border security, an approach that drew criticism from some members of the rank and file who said he was placing his own ambitions ahead of the party's interest. At the same time, Frist has repeatedly called for a comprehensive bill, adopting Bush's rhetoric, and involved himself in the fitful negotiations over the past several days.