President Barack Obama suddenly eased enforcement of the nation's immigration laws Friday, an extraordinary step offering a chance for hundreds of thousands of illegal immigrants to stay in the country and work. Embraced by Hispanics, his action touched off an election-year confrontation with many Republicans.

Mitt Romney, Obama's GOP election foe, criticized the step but did not say he would try to overturn it if elected.

Obama said the change would become effective immediately to "lift the shadow of deportation from these young people."

"Let's be clear, this is not amnesty, this is not immunity, this is not a path to citizenship, this is not a permanent fix," Obama said from the White House Rose Garden. "This is the right thing to do."

The administration said the change will affect as many as 800,000 immigrants who have lived in fear of deportation. It bypasses Congress and partially achieves the goals of the "DREAM Act," legislation that would have provided a pathway to citizenship for young illegal immigrants who went to college or served in the military.

Under the administration plan, illegal immigrants will be able to avoid deportation if they can prove they were brought to the United States before they turned 16 and are younger than 30, have been in the country for at least five continuous years, have no criminal history, graduated from a U.S. high school or earned a GED or served in the military. They also can apply for a work permit that will be good for two years with no limits on how many times it can be renewed.

The move comes in an election year in which the Hispanic vote could be critical in swing states like Colorado, Nevada and Florida. While Obama enjoys support from a majority of Hispanic voters over Republican challenger Romney, Latino enthusiasm for the president has been tempered by the slow economic recovery, his inability to win congressional support for a broad overhaul of immigration laws and by his administration's aggressive deportation policy.

Some Republicans in Congress _ and the governor of Arizona, whose state has been at the center of enforcement controversy _ strongly criticized the Obama action. But the response from Romney was more muted.

Romney said Obama's decision will make finding a long-term solution to the nation's immigration issues more difficult. But he also said the plight of illegal immigrants who were brought to the U.S. as children is "an important matter to be considered."

During the Republican presidential primaries, Romney said he would veto the DREAM Act with its pathway to citizenship.

Obama's new policy tracks a proposal being drafted by Republican Sen. Marco Rubio of Florida, a potential vice presidential running mate for Romney, as an alternative to the DREAM Act, formally the Development, Relief and Education of Alien Minors Act.

Rubio said, "Today's announcement will be welcome news for many of these kids desperate for an answer." But, like Romney, he said it was "a short-term answer to a long-term problem," and he added, "By once again ignoring the Constitution and going around Congress, this short-term policy will make it harder to find a balanced and responsible long-term one."

The change in enforcement policy, to be carried out by the Department of Homeland Security, comes one week before Obama plans to address the National Association of Latino Elected and Appointed Officials' annual conference in Orlando, Fla. Romney is to speak to the group on Thursday.

Making his case on humanitarian grounds, Obama said, "These are young people who study in our schools, they play in our neighborhoods, they're friends with our kids, they pledge allegiance to our flag. They are Americans in their heart, in their minds, in every single way but one: on paper."

The political appeal for many of America's Hispanics was clear. The president and CEO of the National Council of La Raza, Janet Murguia, said, "When it comes to the Hispanic community, this action is a political plus" for Obama. "It's always good to be able to point to your track record and move the needle toward a promise that you made."

In Los Angeles, immigrant students and their supporters rallied at a downtown street to celebrate the announcement, briefly blocking a freeway entrance ramp.

The change drew a swift repudiation from Republican lawmakers, who accused Obama of circumventing Congress in an effort to boost his political standing and of favoring illegal immigrants over unemployed U.S. citizens.

"President Obama and his administration once again have put partisan politics and illegal immigrants ahead of the rule of law and the American people," Rep. Lamar Smith of Texas, GOP chairman of the House Judiciary Committee, said in a statement.

And Rep. Steve King of Iowa, a long time hardliner on immigration issues, said he planned to file suit to halt the policy.

Still, neither House Speaker John Boehner nor Senate Republican leader Mitch McConnell addressed the issue, underscoring the difficulty for Republican leaders as they walk a fine line of trying to appeal to the nation's fastest-growing minority group while not alienating their conservative base.

In Arizona, Gov. Jan Brewer said the change represented a "pre-emptive strike" before an upcoming Supreme Court ruling that could uphold parts of the state's tough immigration enforcement law. She also said the new policy would muddy the waters for Arizona's enforcement efforts.

Many Republicans, including Romney, say they want tighter border security measures before they will consider changes in immigration law. Romney opposes offering legal status to illegal immigrants who attend college but has said he would do so for those who serve in the armed forces.

Praise for the new policy was also swift. Members of the Congressional Hispanic Caucus applauded the move as long overdue. Sen. Dick Durbin of Illinois, the No. 2 Senate Democrat, called the decision "an historic humanitarian moment" and compared it to the decision two decades ago to give political asylum to Cuban refugees fleeing the communist island. "This is at least a reflection of that moment in history."

In New York, Mayor Michael Bloomberg said, "Ending deportations of innocent young people who have the potential to drive tomorrow's economy is long overdue, as are many commonsense reforms needed to center our immigration policy around our economic needs."

Midway through his remarks, Obama was interrupted by a reporter from a conservative online publication, Neil Munro of the Daily Caller, who shouted, "Why do you favor foreigners over American workers?" Clearly irritated, Obama said that he was explaining the policy, not looking for an argument, and that the change was the "right thing to do for the American people."

Obama in the past has resisted pressure to use his executive authority to relax deportations in such a broad manner. The administration had been reviewing deportations on a case-by-case basis, and officials said they concluded that by using the same authority they could help a larger swath of immigrants while at the same time helping unclog immigration courts.

Homeland Security Secretary Janet Napolitano said the decision "is well within the framework of our existing laws."

The Obama administration's deportation policies have come under fire, and Latino leaders have raised the subject in private meetings with the president. In 2011, Immigration and Customs Enforcement deported a record 396,906 people and is expected to deport about 400,000 this year.

A December poll by the Pew Hispanic Center showed that 59 percent of Latinos disapproved of the president's handling of deportations.

The administration announcement comes ahead of an expected Supreme Court decision on Arizona's tough 2010 immigration law that, among other things, requires police to ask for immigration papers from anyone they stop or arrest and suspect is in the country illegally. The Obama administration has challenged the law.