WASHINGTON – Republicans introduced a last-minute alternative immigration reform plan last night, as senators feared hitting an Easter recess deadline without having resolved their differences.

With legalization of America’s estimated 12 million illegal immigrants the key point of contention among Republican lawmakers, the Republican senators’ new plan is an attempt to escape charges that they are offering an amnesty.

Instead of allowing all illegal immigrants who arrived more than two years ago a path to citizenship, those who arrived between two and five years ago would have to return to a port of entry and be subject to green card limits. Illegal immigrants who have been in America for less than two years would not be eligible under either bill.

The move will divert Republicans from responding to a showdown vote the senators set up on a bipartisan immigration bill crafted by Senator McCain, a Republican of Arizona, and Senator Kennedy, a Democrat of Massachusetts. That bill, which passed the Judiciary Committee last week, would create a new guest worker program and allow illegal immigrants who arrived before January 2004 a path to citizenship as long as they fulfill certain requirements, such as paying a $2,000 fine and learning English.

The alternative plan, written by Senator Hagel, a Republican of Nebraska, and Senator Martinez, a Republican of Florida, would keep those requirements but reduce the number of illegal immigrants who can apply for the status to those who have already set down roots in America.

The eleventh hour intervention followed a day in which senators negotiated behind closed doors and on the floor the sensitive issue of how to balance security with solving the rapidly escalating problem of illegal immigration. With election-year politics casting a long shadow, many Republicans invoked the failure of the last attempt to rework the nation’s immigration laws, an amnesty in 1986, as a warning against the current plan.

Florida’s governor, Jeb Bush, who is married to a Mexican, weighed in on the debate, calling it “hurtful” and asking Congress to take swift action.”The cumulative effect of some politicians pounding their chests about immigration is hurtful to both of us,” Mr. Bush wrote, according to the Los Angeles Times, referring to himself and his brother, President Bush. “I fear they do so for current political gain at the expense of thoughtful policy over the long term.”

An aide for Senator Frist said he believed the competing bill had enough Republican support to ensure its passage. The question now appears to lie with the Democrats who had tried to prevent additional amendments. Some in the majority said the division had switched parties, with Democrats buckling to pressure from organized labor.

“There has been a change in this debate,” Senator Graham, a Republican of Florida, said. “The closer we get to really solving this problem, what was a subtle pushback last week is now all out open warfare.”

According to both the McCain-Kennedy bill and the new alternative, 400,000 new guest workers will be admitted per year to fill jobs for which Americans could not be found. They would then be eligible for six-year visas after which they could apply for a capped number of green cards.

On Tuesday, when Senator McCain spoke to some members of AFL-CIO leadership promoting the bill he was booed. To shouts of “pay a decent wage,” McCain responded that the union brass assembled, members of the AFL-CIO’s Building and Construction Trades Department wouldn’t pick lettuce for a season for $50 an hour. “You can’t do it, my friends,” he said of such menial labor.

Senator Durbin of Illinois, the second-ranking Democrat, denied divisions were undoing the Democrats. Instead, he warned that if the Republicans did not work with the Democrats to pass legislation, voters would fault them at the polls.

“If the Republican Party decides to oppose this,” Mr. Durbin said of passing an immigration reform bill, “it will be remembered for a long time.” He also vowed members of his party would fight “tooth and nail” if the Republicans tried to pass an enforcement-only bill as the House did late last year.

The president of the National Hispanic Christian Leadership Conference, Samuel Rodriguez, said, “There are definitive ramifications if there is only border security and enforcement,” noting Hispanic Republicans were key in electing President Bush and are the fastest-growing segment of the Republican Party.