WASHINGTON (Reuters) - A bipartisan group of U.S. senators has agreed on an immigration reform plan that would provide a path to citizenship for the 11 million illegal immigrants in the United States but only after borders are better secured. The plan, unveiled a day before President Barack Obama is to give a policy speech on immigration in Nevada, tackles the most explosive issue - how to deal with the millions of foreigners living in the United States illegally. 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, according to the document by eight Senators including Republicans Marco Rubio of Florida, John McCain and Jeff Flake of Arizona and Lindsey Graham of South Carolina, and Democrats Charles Schumer of New York, Dick Durbin of Illinois, Michael Bennet of Colorado and Robert Menendez of New Jersey. The White House praised the group's efforts but warned that Obama would not be satisfied until there was meaningful reform. The president "will continue to urge Congress to act until that is achieved," a White House spokesman said. Lawmakers have scheduled a news conference for 2:30 p.m. Under the plan, no one would be given more permanent legal status until new measures were implemented to stem the flow of immigrants across U.S. borders, a critical concession to conservatives and border state members of congress. The path to citizenship would also be contingent on a new enforcement measure to track the status of immigrants who may have overstayed visas, the document said. The proposal resembles previous immigration bills - including a 2007 measure that died in Congress in part because of disagreement over the timing and balance of border-enforcement measures versus granting citizenship to the millions of undocumented immigrants. But advocates noted that this time, the climate was ripe for immigration reform. Conservatives, law enforcers and businesses are calling for immigration reform. You did not see that in 2007," said Ali Noorani, the executive director with the National Immigration Forum advocacy group. Democrats have considered future citizenship for undocumented immigrants a "bottom line" for a bill, as Schumer said Sunday at a news conference. Republicans, in turn, have tended to stress border security. While the framework released Monday includes something for all these groups, translating the four-page outline into legislation with a chance of passing is likely to prove challenging, notwithstanding the bi-partisan makeup of the group and support that came early Monday from U.S. Senate Majority Leader Harry Reid. Rubio's involvement has helped give the plan credibility among some Republicans. His proposals have attracted support from influential conservatives, including former vice presidential nominee Paul Ryan and TV commentator Bill O'Reilly. Last year, Rubio had a hard time getting conservatives on board for allowing "dreamers" to stay here - children of illegals, many of whom have spent most of their lives in the United States, are in the country through no fault of their own and attend U.S. schools. Rubio is a Cuban-American who is often mentioned as a presidential contender. He is a favorite of the Tea Party conservative movement. In addition to the path to citizenship, the Senators' proposal outlines three other legislative goals: retaining and attracting highly qualified workers; creating a system to prevent identity theft and the hiring of unauthorized workers: and establishing a way to bring in unskilled labor while providing them with workers rights. The immigration issue was largely pushed aside during Obama's first term as he tackled healthcare and the economy. But the president, who had overwhelming support from Hispanic voters in his 2012 re-election, cited it as part of his agenda when sworn in for a second term last week. Immigration has been among the toughest issues confronting Congress over the past two decades, in part because so many powerful interest groups have a stake in it, from business organizations in need of skilled labor to the trade union movement, which worries that a flow of immigrant labor unprotected by U.S. workplace laws could depress wages. The U.S. Chamber of Commerce has made immigration reform a priority this year, expressing particular support for provisional visas for lesser-skilled workers and expansion of green cards for foreign nationals who receive advanced degrees from U.S. colleges and universities. On Monday, the Chamber praised the proposal and said it would work with all parties to get a bill passed. Additional reporting by Jeff Mason; Editing by Fred Barbash and Philip Barbara