LAS VEGAS -- Seizing on a groundswell of support for rewriting the nation's immigration laws, President Obama challenged Congress on Tuesday to act swiftly to put 11 million illegal immigrants living in the United States on a clear path to citizenship.
He also praised a bipartisan group of senators, who proposed their own sweeping immigration overhaul a day earlier, saying their plan was very much in line with his own proposals, and suggested there was a "genuine desire to get this done soon."
Speaking at a high school here, Mr. Obama said, "The good news is that for the first time in many years, Republicans and Democrats seem ready to tackle this problem together."
But Mr. Obama warned that "the closer we get, the more emotional this debate is going to become." He said that if Congress did not act quickly enough on its own legislation, he would send up a bill -- something the White House has put off for now.
There were hints in Mr. Obama's speech of potential fault lines in the debate. He declared, for example, that there must be a path to citizenship for illegal immigrants "from the outset." That would seem at odds with the assertion by some senators that citizenship must be tied to tighter border security.
Although Mr. Obama did not say it in his speech, the White House is also proposing that the United States treat same-sex couples the same as other families, meaning that people would be able to use their relationship as a basis to obtain a visa.
Mr. Obama offered a familiar list of proposals: tightening security on borders, cracking down on employers who hire undocumented workers and temporarily issuing more visas to clear the huge backlog of people applying for legal status in the country.
His speech, on the heels of the bipartisan Senate proposal, sets the terms for one of the year's landmark legislative debates. These are only the opening steps in a complicated dance, and the effort could still founder, as did the effort to overhaul immigration laws in the George W. Bush administration.
But the flurry of activity underscores the powerful new momentum behind an overhaul of the immigration system, after an election that dramatized the vulnerability of Republicans on the issue, with Mr. Obama piling up lopsided majorities over Mitt Romney among Hispanic voters.
"Most Americans agree that it's time to fix a system that's been broken for too long," Mr. Obama said to an audience of about 2,000 high school students, many of them Hispanic, who applauded loudly when he mentioned the Dream Act, which offers amnesty to children of immigrants who are in the United States illegally.
In scrambling to present their blueprint on Monday, the day before Mr. Obama's speech, the senators stole a march on the president. But their intent appeared less to undermine his efforts than to stake out their own role in drafting a comprehensive bill.
"It is a fascinating Washington horse race that you don't always see, and a signal of the seriousness to get across the finish line," said Angela Kelly, an expert on immigration at the Center for American Progress.
With the senators hoping to pass legislation by this summer, the White House has shelved, for now, plans to introduce its own immigration bill, officials said. Indeed, after two years of feuding with Congress, Mr. Obama finds himself in rare alignment with Democratic and Republican lawmakers on a major issue.
That is what made Mr. Obama's speech such a novelty: Rather than criticize a do-nothing Congress for its obstructionism, as he did nearly every day during the campaign, he applauded the lawmakers for racing ahead of him, at least for a day.
Beneath the expressions of harmony, however, Ms. Kelly cautioned; "There's so much they don't agree on. There's going to be a lot of soul-searching."
Among the key differences is whether to make the path to citizenship for illegal immigrants contingent on stricter border controls and visa procedures.
Republicans like Senator Marco Rubio of Florida are insisting on such requirements to prevent a new influx of illegal immigrants, as happened after immigration was last overhauled in 1986 during the Reagan administration.
But Mr. Obama, in his remarks, emphasized that as long as immigrants registered with the authorities, paid taxes and any fines, learned English and passed criminal background checks, there should be no doubt that they would eventually obtain citizenship.
"If you're able to meet some basic criteria," he said, "we'll offer you the chance to come out of the shadows."
That will be difficult for many Republicans to accept, particularly those from districts where the debate is cast in terms of offering "amnesty" to illegal immigrants. Mr. Rubio, a Cuban-American, who has emerged as a leading voice on this issue, has insisted that a pathway to citizenship be tied to tougher enforcement.
Mr. Obama defended his record in securing the borders, noting that the administration had doubled the number of Border Patrol agents since 2004 and had built hundreds of miles of fences, reducing the number of people trying to cross illegally. Six unmanned surveillance drones now fly over the southwest border, in addition to 124 other aircraft.
Mr. Obama's remarks differed little from the main points in his 29-page blueprint for overhauling immigration laws, which he issued last May and used a plank in his re-election campaign. But his language was plainer and more forceful -- speaking of a road to citizenship for illegal immigrants, for example, not merely a road to legal status.
The provision on same-sex couples was not in the blueprint, though an administration official said the Department of Homeland Security began using it in deciding cases involving families in 2010.
The president's goal, the officials said, will be less to underline differences with the bipartisan plan than to marshal public support behind comprehensive immigration legislation. Mr. Obama, having failed to achieve that in his first term, has put it at the top of his second-term agenda.
The four pillars in the bipartisan proposal -- border security, employer enforcement, provisions for granting entry to farmworkers and highly skilled engineers, and the pathway to citizenship -- mirror the main components of Mr. Obama's blueprint.
There are plenty of other hurdles ahead. House Republicans are expected to oppose extending benefits to same-sex couples and also resist the concept of offering a path to citizenship for illegal immigrants, though there was talk this week of attempts to find a bipartisan approach in the House as well.
The president's choice of Nevada for the speech underlines the political threat that immigration poses to Republicans. Mr. Obama beat Mr. Romney by more than six percentage points in the state, though Nevada's economy was devastated by the housing collapse. Much of that was due to a surge of support from Hispanics.
A senior administration official said the president's speech was the start of a concerted campaign to force Republicans to follow through on the bipartisan proposal. And he predicted that, given the president's popularity with Hispanic voters, they would find it difficult vote down a bill with his name on it.
In his remarks, Mr. Obama appealed to the history of the United States as a nation of immigrants. "We define ourselves as a nation of immigrants," he said. "That's who we are in our bones."
This article originally appeared in The New York Times.