WASHINGTON — President Barack Obama eased enforcement of immigration laws today, offering a chance for hundreds of thousands of illegal immigrants to stay in the country and work. Immediately embraced by Hispanics, the extraordinary step touched off an election-year confrontation with congressional Republicans.

“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 policy 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,” congressional legislation that would establish a path toward citizenship for young people who came to the United States illegally but who attend college or join the military.

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.

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

The step, 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. Republican presidential challenger Mitt Romney is to speak to the group on Thursday.

“Many of these young people have already contributed to our country in significant ways,” Homeland Security Secretary Janet 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 policy closely 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.