Congressional Republicans anxious to block immigration reform will be paying close attention to President Bush’s State of the Union speech next week, when the president will likely signal his level of commitment to creating a national guest worker program.

Senate Republicans dealt a blow to his plan this week when they did not include immigration as one of their top 10 priorities for the upcoming term. But Mr. Bush asserted at a White House press conference that immigration will be one of his priorities.

“It’s necessary to reform the immigration system,” he said.

The president has offered only broad outlines for a guest worker proposal. It would allow the estimated 10 million undocumented immigrants in America to gain three-year renewable temporary work visas. Employers could also advertise for foreign workers and the government would provide guest worker visas if they can prove a labor shortage.

“I’m against amnesty, I’ve made that very clear,” Mr. Bush said yesterday. Instead, he said, he is “advancing a program that enables people to come into our country in a legal way to work for a period of time, for jobs that Americans won’t do, will help make it easier for us to secure our borders.”

But before he can move forward with this program, Mr. Bush will have to fight for his own party’s support.

“Immigration is to Republicans what trade has been to Democrats. It’s the issue that divides the party, and it’s not predictable where individuals stand,” said Marshall Wittmann, a senior fellow at the Democratic Leadership Council and a former spokesman for Senator McCain.

With the Republican Party about evenly spit on the issue, and most Democrats supporting some sort of reform, “there are many on the Hill who will be deeply disappointed if he does not make it a priority issue,” Mr. Wittmann said. “From the time he ran for president back in 2000, he has made this a centerpiece issue that defined him as a compassionate conservative, and there would be a lot of disappointment if he dropped it and did not raise it in the State of the Union address.”

Even Rep. Tom Tancredo, a Republican from Colorado who leads the immigration-reform caucus in the House and has vowed to block the president’s proposal, said he expects to hear about immigration from the president in his address. Still, he said, he is increasingly certain Republican congressmen will block its passage.

“I’ve been crying wolf now for six years. And now I can finally say that the tide is turning,” Mr. Tancredo said, noting an increase in Republicans voicing dissatisfaction with the proposal since the election. “This is the first time I could ever tell a reporter that my side of the debate is now on the offensive, and they are trying to find ways to stop us.”

In fact, in a move to crack down on undocumented immigrants, the chairman of the House Judiciary Committee, James Sensenbrenner, yesterday introduced border and document security legislation. Called the Real ID bill, the proposal contains immigration provisions that were dropped from the September 11 commission legislation, including a provision that would restrict driver’s licenses to American citizens.

A former speechwriter for President Bush, David Frum, said the immigration debate has an enormous potential to divide the Republican Party.

“I think the only question is how much damage [the president] will do to the Republican Party before he eventually drops the idea,” said Mr. Frum, a resident fellow at the American Enterprise Institute. “I don’t think anything like his plan can get through Congress. Which is not to say that pieces cannot, because there are some very good pieces, but his plan as a whole offers very little to those who support greater enforcement, and they have a significant presence in Congress.”

Mr. Bush first introduced the plan more than a year ago. But it generated strong opposition from his own party, and he rarely addressed immigration until after the election. Recently, he has become more outspoken on the issue, repeatedly stating his commitment to reform. He also reportedly told Senator McCain he would support bipartisan legislation the Arizona senator is writing with Senator Kennedy of Massachusetts.

“He’s sending really clear messages,” said Angela Kelley, the deputy director of the National Immigration Forum, a pro-immigrant advocacy group.

Still, analysts agree the State of the Union speech will indicate to what degree the president will push for immigration reform, which must compete with other issues such as Social Security, the Middle East, and tax reform for a place on the congressional agenda.

“His decision whether to include it or not to include it can be a very important indicator,” Mr. Frum said. “If it’s not, I think we can assume the idea has been disregarded. If it does, he is prepared to invest some energy.”

A growing and broad alliance of unlikely bedfellows – from organized labor to business leaders to immigration groups – has voiced support for the president’s proposal.

But without the president making a clear commitment to providing legal status to the undocumented immigrants already here, many immigration-reform groups are saying that more details are needed before they can support it.

“What we’d like to see is a three pronged approach,” said the director of migration and refugee policy of the U.S. Council of Catholic Bishops, Kevin Appleby. It includes outlining a legalization program for those living here illegally, reforming the family-based program to cut back on backlogs, and creating a worker program in the spirit of the president’s, he said.

“The president’s proposal falls short because it addresses only one aspect of that and does that in an inadequate fashion,” he said. “We hope that he will expand on his proposal this year.”