The policy change, described to The Associated Press by two senior administration officials, will affect as many as 800,000 immigrants who have lived in fear of deportation. It also bypasses Congress and partially achieves the goals of the so-called DREAM Act, a long-sought but never enacted plan to establish a path toward citizenship for young people who came to the United States illegally but who have attended college or served in the military.

Homeland Security Secretary Janet Napolitano was to announce the new policy Friday, one week before President Barack Obama plans to address the National Association of Latino Elected and Appointed Officials’ annual conference in Orlando, Fla. Republican presidential challenger Mitt Romney is scheduled to speak to the group on Thursday.

Obama planned to discuss the new policy Friday afternoon from the White House Rose Garden.

Under the administration plan, illegal immigrants will be immune from deportation if 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 officials who described the plan spoke on the condition of anonymity to discuss it in advance of the official announcement.

The policy will not lead toward citizenship but will remove the threat of deportation and grant the ability to work legally, leaving eligible immigrants able to remain in the United States for extended periods. It tracks closely to a proposal offered by Republican Sen. Marco Rubio of Florida as an alternative to the DREAM Act.

“Many of these young people have already contributed to our country in significant ways,” Napolitano wrote in a memorandum describing the administration’s action. “Prosecutorial discretion, which is used in so many other areas, is especially justified here.”

The extraordinary 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, 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. Activists opposing his deportation policies last week mounted a hunger strike at an Obama campaign office in Denver, and other protests were planned for this weekend.

The change is likely to cause an outcry from congressional Republicans, who are sure to perceive Obama’s actions as an end run around them. Republicans already have complained that previous administration uses of prosecutorial discretion in deportations amount to back-door amnesty. Romney and many Republican lawmakers want tighter border security measures before considering 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.

An NBC News/Wall Street Journal poll last month found Obama leading Romney among Hispanic voters 61 percent to 27 percent. But his 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 changes come a year after the administration announced plans to focus on deporting serious criminals, immigrants who pose threats to public safety and national security, and serious immigration law violators.

One of the officials said the latest policy change is just another step in the administration’s evolving approach to immigration.

Under the plan, immigrants whose deportation cases are pending in immigration court will have to prove their eligibility for a reprieve to ICE, which will begin dealing with such cases in 60 days. Any immigrant who already has a deportation order and those who never have been encountered by immigration authorities will deal with the U.S. Citizenship and Immigration Services.

The exact details of how the program will work, including how much immigrants will have to pay to apply and what proof they will need, still are being worked out.

In making it harder to deport, the Obama administration is in essence employing the same eligibility requirements spelled out in the proposed DREAM Act.

The administration officials stopped short of calling the change an administrative DREAM Act — the name is an acronym for Development, Relief and Education for Alien Minors — but the qualifications meet those laid out in a 2010 version that failed in the Senate after passing in the House. They said the DREAM Act, in some form, and comprehensive overhaul of the immigration system remained an administration priority.

Illegal immigrant children won’t be eligible to apply for the deportation waiver until they turn 16, but the officials said younger children won’t be deported either.

Last year, Napolitano announced plans to review about 300,000 pending deportation cases and indefinitely suspend those that didn’t meet department priorities. So far, Immigration and Customs Enforcement has reviewed more than 232,000 cases and decided to stop working on about 20,000. About 4,000 of those 20,000 have opted to keep fighting in court to stay in the United States legally. For the people who opted to close their cases, work permits are not guaranteed.