April 6 (Bloomberg) -- Senate Republicans and Democrats reached an agreement on procedures for allowing undocumented aliens to apply for citizenship, clearing an obstacle that stalled legislation overhauling U.S. immigration laws.

``We have a huge breakthrough,'' Senate Majority Leader Bill Frist of Tennessee told reporters today.

The Senate is working to pass an overhaul of immigration policies that includes strengthening border security and creating a guest-worker program, before a two-week recess begins at the end of this week. Debate on the measure had stalled as Republicans negotiated how to treat undocumented immigrants and Democrats worked to block amendments they said were too harsh.

Democrats, including Senator Ted Kennedy of Massachusetts and Minority Leader Harry Reid, said today's compromise may lead to passage of the Senate measure this week. Still, negotiations continue on amendments, and any Senate measure will have to be reconciled with House legislation that focuses on border security.

``It's not a done deal by any stretch of the imagination,'' said Democrat Charles Schumer of New York.

Three Groups

The compromise splits the estimated 11 million undocumented immigrants into three groups, based on how long they have been in the U.S., for the purpose of setting rules on their eligibility to apply for legal status.

Under the plan hammered out by Republicans last night, the more than 1 million undocumented immigrants who entered the U.S. after Jan. 7, 2004, would have to return to their home countries and apply for a new guest-worker program from there.

The estimated 3 million immigrants who illegally entered between 2001 and 2004 would have three years to apply for legal status as part of a new temporary-worker program and pay as much as $3,000 in fines. To receive their temporary-worker visas, they would have to travel to a land port of entry and physically leave the U.S. before immediately re-entering.

Once they receive the visas, they could stay as long as six years while applying for permanent residency. As part of the compromise with Democrats enough residency cards would be available to ensure all of the immigrants who wanted to stay in the U.S. could. The Republican measure had limited their number to 130,000 per year.

Undocumented immigrants who have been in the U.S. more than five years, an estimated 7 million people, would be able to keep their jobs after paying a $2,000 fine and meeting other criteria, such as learning English.

Republican Opposition

President George W. Bush, speaking to reporters at an airport in Charlotte, North Carolina, after a speech, stopped short of endorsing the plan, while commending senators for ``working together to get a comprehensive immigration bill.''

Some Republicans said they remain opposed. ``It's unacceptable to me,'' Republican Jeff Sessions of Alabama said. ``We're not ready to do this right now.''

Texas Senator John Cornyn said senators may become ``uncomfortable,'' as they read the provisions of the legislation and it is ``premature'' to talk about how many may oppose it.

Under the agreement, all undocumented immigrants in the U.S. for more than five years would be able to acquire legal residency and U.S. citizenship after about 11 years while it would take about two years longer for those here between five years and two years. Family members of workers would also be eligible.

As part of the agreement with Democrats, the number of guest-worker visas was reduced from 400,000 per year to 325,000 per year. Employers would have to spend 60 days trying to find a U.S. worker before they could hire an immigrant.

The Senate plan would set up a clash with the House measure, which proposes a 700-mile border fence and doesn't create a guest-worker program or address the legal status of immigrants.

`Dysfunctional'

``Members of Congress, especially Republicans, are beginning to realize that around the country, even among their supporters, they're being viewed as dysfunctional, unable to get anything done,'' said Greg Valliere, chief political strategist at Stanford Washington Research in Washington. ``So I think the Republicans are starting to come together, at least a little in the Senate on immigration.''

Colorado Republican Representative Tom Tancredo, chairman of the 96-member House Immigration Reform Caucus, called the compromise ``miserable public policy.''

``I do not believe that a plan of this nature can pass the House,'' he said.

Senate Democrats said they would support the Senate compromise as long as it isn't undermined by amendments that are too harsh and they have commitments that it won't be significantly changed in negotiations with the House.

``We're trying to figure out some mechanism by which we can have an assurance that the bill that we've agreed to is actually the bill that gets voted on and is the bill that the president signs,'' Democrat Barack Obama of Illinois said.

To contact the reporter on this story: Nicholas Johnston in Washington at njohnston3@bloomberg.net

Last Updated: April 6, 2006 17:41 EDT