Historic U.S. immigration legislation cleared a key Senate hurdle with votes to spare on Monday, pointing the way to near-certain passage within days for stepped up security along the border with Mexico and a chance at citizenship for millions living in the country illegally.

The vote was 67-27, seven more than the 60 needed, with 15 Republicans voting to advance legislation at the top of President Barack Obama's second-term domestic agenda.

The vote came as Obama campaigned from the White House for the bill, saying, ``now is the time'' to overhaul an immigration system that even critics of the legislation agree needs reform.

Immigration reform is possibly Obama's best chance at a major domestic accomplishment during his second term, following setbacks for his administration on gun control and fiscal issues.

But with Republicans divided on the issue, the immigration bill faces a tough battle in the House of Representatives, even if it passes in the Senate later this week.

Many Republicans say the immigration bill offers the party a chance to show a more welcoming face to Hispanic voters, an increasingly vital constituency that largely supported Obama and the Democrats in the November elections.

Many conservative Republicans in the House majority, however, assail as amnesty for those who have violated the law.

Last-minute frustration was evident among opponents. In an unusual slap at members of his own party as well as Democrats, Republican Sen. Ted Cruz of Texas said it appeared that lawmakers on both sides of the political aisle ``very much want a fig leaf'' on border security to justify a vote for immigration.

Some Republican lawmakers have appealed to the leader of the House, Speaker John Boehner, not to permit any immigration legislation to come to a vote for fear that whatever its contents, it would open the door to an unpalatable compromise with the Senate. At the same time, the House Judiciary Committee is in the midst of approving a handful of measures related to immigration, action that ordinarily is a prelude to votes in the full House.

Obama made clear he hoped that a big victory for immigration in the Senate would ease its passage in the House.

``Now is the time to do it,'' Obama said at the White House before meeting with nine business executives who support a change in immigration laws. He added, ``I hope that we can get the strongest possible vote out of the Senate so that we can then move to the House and get this done before the summer break'' beginning in early August.

He said the measure would be good for the economy, for business and for workers who are ``oftentimes exploited at low wages.''

Opponents saw it otherwise. ``It will encourage more illegal immigration and must be stopped,'' Cruz exhorted supporters via email, urging them to contact their own senators with a plea to defeat the measure.

The non-partisan Congressional Budget Office has estimated the legislation will reduce the deficit and increase economic growth in each of the next two decades. It is also predicting unemployment will rise slightly through 2020, and that average wages will move lower over a decade.

At its core, the legislation in the Senate would create a 13-year pathway to citizenship for an estimated 11 million immigrants living illegally in the United States. It also calls for billions of dollars to be spent on manpower and technology to secure the 2,000-mile border with Mexico, including a doubling of the Border Patrol with 20,000 new agents.

The measure also would create a new program for temporary farm laborers to come into the country, and another for lower-skilled workers to emigrate permanently. At the same time, it calls for an expansion of an existing visa program for highly-skilled workers, a gesture to high tech companies that rely heavily on foreigners.

In addition to border security, the measure phases in a mandatory program for employers to verify the legal status of potential workers, and separate effort to track the comings and goings of foreigners at some of the nation's airports.

The legislation was originally drafted by a bipartisan Gang of 8, four senators from each party who negotiated a series of political tradeoffs over several months. (AP)