WASHINGTON, Jan. 6 — President Bush will propose a sweeping overhaul of the nation's immigration laws on Wednesday that could give legal status to millions of undocumented workers in the United States, senior administration officials said Tuesday night.

Under Mr. Bush's proposal, which effectively amounts to an amnesty program for illegal immigrants with jobs in the United States, an undocumented worker could apply for temporary worker status here for an unspecified number of years, with all the employee benefits, like minimum wage and due process, accorded to those legally employed.

Workers who are approved would be permitted to travel freely between the United States and their home countries, the officials said, and would also be permitted to apply for a green card granting permanent residency in the United States.

Administration officials said that Mr. Bush would also propose increasing the number of green cards issued each year, which is now about 140,000, but they did not provide a specific number. The administration officials, who briefed reporters in a conference call on Tuesday night, said only that Mr. Bush would ask for a "reasonable increase."

Mr. Bush's proposal, one administration official said, would "match willing workers with willing employers" and would "promote compassion" by fixing what one called "a broken system." The officials declined to call it an amnesty program.

Under the proposal, workers in other countries could also apply for guest worker status in the United States, provided there was no American to take the job.

But the president's plans are expected to face a tough fight in Congress, where conservative Republicans have said they consider programs like the one the president is proposing nothing more than amnesty for people who have broken the law.

The president's proposals were designed to appeal to Hispanic groups, a constituency that the White House is focusing on as Mr. Bush seeks re-election this year. The proposals are expected to be embraced by President Vicente Fox of Mexico, who has been lobbying for them for the past three years.

Mr. Bush is to meet with Mr. Fox at an economic summit next week in Monterrey, Mexico, where immigration will be a significant part of the agenda and Mr. Bush's proposals are likely to become a major focus.

Mr. Bush's proposal is closely modeled on legislation introduced last summer by Senator John McCain and Representatives Jim Kolbe and Jeff Flake, all Republicans from Arizona. The issue of illegal workers has been an important one there.

"We are ecstatic that they are addressing this," Mr. Flake said in a telephone interview on Tuesday night. "We've maintained all along that you have to deal with both sides of the issue — those who want to come to the country, and those who are here now. We're very happy to see a realistic approach. We deal with it daily, and we have to have a rational policy."

Mr. Bush's proposal is in some ways more generous to illegal workers than is Mr. Flake's bill. The legislation, for example, requires that a guest worker wait three years before applying for a green card. Under Mr. Bush's proposal, a worker could apply for a green card right away.

Mr. Bush's proposals apply to all illegal immigrants in the United States, which officials estimate at 8 million to 14 million people. About 60 percent are thought to be Mexican. No one is certain how many undocumented workers there are among all illegal immigrants, but Mr. Fox has said that some 3.5 million of the workers are Mexican.

Mr. Bush entered office with immigration reform at the top of his foreign policy agenda, and in the late summer of 2001 various guest worker proposals were under discussion by United States and Mexican officials. But the Sept. 11 terrorist attacks led to increased concerns about the safety of America's borders and derailed the negotiations.

Under Mr. Bush's proposals, an undocumented worker and an employer would have to apply for the guest worker program hand in hand, with the employer serving as the sponsor for the worker. There would also be a fee to register for the program, but officials would not say how much that would be.

The plan also includes incentives for workers to return to their countries, like a promise of retirement benefits there based on income earned in the United States.

Critics of Mr. Bush's proposal noted that unless the White House sought, and obtained, a large increase in the number of green cards issued each year, many of the undocumented workers who apply under the president's program could face an extended wait for residency, 10 to 20 years, by some estimates.

Administration officials acknowledge that the wait for a green card could take up to six years or longer, meaning that some guest workers who apply for green cards but do not receive them before their guest worker status expires would face the prospect of being forced to leave the United States. In that case, critics of the proposal said Tuesday night, workers would be better off remaining illegal and staying indefinitely in the United States, rather than revealing themselves to immigration officials when they sign up for a program that may, these critics assert, lead to their deportation.

"They're asking people to sign up for a program that is more likely to ensure their departure than ensure their permanent residency," said Cecilia Muñoz, a vice president of the National Council of La Raza, a Hispanic advocacy organization.

Administration officials declined to say how long people could remain in the guest worker program. But Ms. Muñoz said congressional officials briefed on the program told her they were led to believe that it could be no longer than six years.

Groups opposed to increased immigration also criticized the president's proposal. "It's an amnesty, no matter how much they dance around the fact," said Mark Krikorian, executive director of the Center on Immigration Studies, a group that seeks to limit immigration. "It's legalizing illegal immigrants."

Other critics say that the guest worker program could lead to the exploitation of immigrant workers. "If you are dependent on an employer filing a petition on your behalf, that employer has a tremendous club over you," one person briefed on the president's proposal said.

But an administration official said that the plan would protect the rights of undocumented workers, "who now live in the shadows, and are fearful of coming out of the shadows."

A number of limited guest worker programs already exist in the United States, but they are designed for skilled technology workers, who typically come from India, China and Eastern Europe.

Mr. Bush will also argue, administration officials said, that his plan will make the country safer by giving the authorities a better idea of who is in the country and crossing its borders.