The nation’s two major labor federations have agreed for the first time to join forces to support an overhaul of the immigration system, leaders of both organizations said on Monday. The accord could give President Obama significant support among unions as he revisits the stormy issue in the midst of the recession.

John Sweeney, president of the A.F.L.-C.I.O., and Joe T. Hansen, a leader of the rival Change to Win federation, will present the outlines of their new position on Tuesday in Washington. In 2007, when Congress last considered comprehensive immigration legislation, the two groups could not agree on a common approach. That legislation failed.

The accord endorses legalizing the status of illegal immigrants already in the United States and opposes any large new program for employers to bring in temporary immigrant workers, officials of both federations said.

“The labor movement will work together to make sure that the White House as well as Congress understand that we speak about immigration reform with one voice,” Mr. Sweeney said in a statement to The New York Times.

But while the compromise repaired one fissure in the coalition that has favored broad immigration legislation, it appeared to open another. An official from the United States Chamber of Commerce said Monday that the business community remained committed to a significant guest-worker program.

“If the unions think they’re going to push a bill through without the support of the business community, they’re crazy,” said Randel Johnson, the chamber’s vice president of labor, immigration and employee benefits. “There’s only going to be one shot at immigration reform. As part of the trade-off for legalization, we need to expand the temporary worker program.”

The common labor position is also unlikely to convince many opponents that an immigration overhaul would not harm American workers. When Obama administration officials said last week that the president intended to push Congress this year to take up an immigration bill that would include a path to legal status for the country’s estimated 12 million illegal immigrants, critics criticized the approach as amnesty for lawbreakers.

“In our current economic crisis, Americans cannot afford to lose more jobs to illegal workers,” said Representative Steve King, an Iowa Republican who sits on the House Judiciary subcommittee on immigration. “American workers are depending on President Obama to protect their jobs from those in America illegally.”

The two labor federations have agreed in the past to proposals that would give legal status to illegal immigrants. But in 2007 the A.F.L.-C.I.O. parted ways with the service employees and several other unions when it did not support legislation put forth by the Bush administration because it contained provisions for an expanded guest-worker program.

In the new accord, the A.F.L.-C.I.O. and Change to Win have called for managing future immigration of workers through a national commission. The commission would determine how many permanent and temporary foreign workers should be admitted each year based on demand in American labor markets. Union officials are confident that the result would reduce worker immigration during times of high unemployment like the present.

Mr. Hansen, who is president of the United Food and Commercial Workers Union, said in an interview that the joint proposal was a “building block to go forward to get immigration reform up on the agenda in Congress” sometime this year.

Thousands of immigrant farm workers and other low-wage laborers come to the United States through seasonal guest-worker programs that are subject to numerical visa limits and have been criticized by employers as rigid and inefficient. Many unions oppose the programs because the immigrants are tied to one employer and cannot change jobs no matter how abusive the conditions, so union officials say they undercut conditions for American workers. Highly skilled foreign technology engineers and medical specialists also come on temporary visas.

Advocates for immigrants said a unified labor movement could substantially bolster their position as they push for legislation to restructure the ailing immigration system.

“It shows how important the issue is to the representatives of American workers,” said Frank Sharry, executive director of America’s Voice, an advocate group.

A.F.L.-C.I.O. officials said they agreed with Change to Win leaders that, with more than seven million unauthorized immigrants already working across the nation, legalizing their status would be the most effective way to protect labor standards for all workers.

“We have developed a joint strategy with the approach framed around workers’ rights,” said Ana Avendaño, associate general counsel of the A.F.L.-C.I.O.

Labor leaders said that they would talk with other groups in coming weeks to nail down details of a common position, and that they would then would work in Congress and with the Obama administration to try to ensure that their proposal was part of any bill offered for debate.

Also supporting the compromise is Eliseo Medina, an executive vice president of the Service Employees International Union, a member of Change to Win with hundreds of thousands of members who are immigrants. The Change to Win federation was formed in 2005 with seven unions that broke away from the A.F.L.-C.I.O.

The plan for a labor commission to monitor and control levels of worker immigration was developed with help from Ray Marshall, a labor secretary under President Jimmy Carter. Over the past year, Mr. Marshall, at the request of the A.F.L.-C.I.O., has been consulting between the two federations and with a variety of Hispanic organizations and advocate groups for immigrants.

“All these groups understand that one of the main reasons they lost before was that they were not together,” Mr. Marshall said.

According to a list of principles the labor leaders will present on Tuesday, they are proposing a “depoliticized,” independent commission that “can assess labor market needs on an ongoing basis and — based on a methodology to be approved by Congress — determine the number of foreign workers to be admitted for employment purposes.”

Mr. Johnson, the Chamber of Commerce official, said, “A commission doesn’t get us there.”

Tamar Jacoby, president of ImmigrationWorks USA, a group that organizes businesses to support comprehensive immigration legislation, agreed that employers would have many questions about the approach.

“The question is, Will the commission work?” Ms. Jacoby said. “Will it be adequately attuned to and triggered by the labor market? A system that may — or may not — supply the workers that business will need in the future after the recession will be a cause of great concern to employers.”