Administration officials said the president used existing legal authority to make the broad policy change, which could temporarily benefit more than 800,000 young people. He did not consult with Congress, where Republicans have generally opposed measures to benefit illegal immigrants.
The policy, while not granting any permanent legal status, clears the way for young illegal immigrants to come out of the shadows, work legally and obtain driver’s licenses and many other documents they have lacked.
“They are Americans in their heart, in their minds, in every single way but one: on paper,” President Obama said in announcing the new policy in the White House Rose Garden on Friday. He said he was taking “a temporary stopgap measure” that would “lift the shadow of deportation from these young people” and make immigration policy “more fair, more efficient and more just.”
Under the change, the Department of Homeland Security will no longer initiate the deportation of illegal immigrants who came to the United States before age 16, have lived here for at least five years, and are in school, are high school graduates or are military veterans in good standing. The immigrants must also be under 30 and have clean criminal records.
Young people, who have been highly visible and vocal activists despite their undocumented status, have been calling on Mr. Obama for more than a year to stop deporting them and allow them to work. Many of them were elated and relieved on Friday.
“People are just breaking down and crying for joy when they find out what the president did,” said Lorella Praeli, a leader of the United We Dream Network, the largest coalition of illegal immigrant students.
Republicans reacted angrily, saying the president had overstepped his legal bounds to do an end run around Congress. Some Republicans accused Mr. Obama of violating the law. “The president’s action is an affront to the process of representative government by circumventing Congress and with a directive he may not have the authority to execute,” said Senator Charles E. Grassley of Iowa, the senior Republican on the Senate Judiciary Committee. “It seems the president has put election-year politics above responsible policies.”
In many ways, the president’s move was a clear play for a crucial voting bloc in states that will decide whether he gets another term. It also held the potential for considerable payoff.
The action was the first measure by Mr. Obama that offers immediate relief to large numbers of illegal immigrants, in contrast to smaller steps the administration had taken that were intended to ease the impact of deportations but in practice had little effect. During the three years of his term, Mr. Obama has deported more than 1.1 million immigrants, the most by any president since the 1950s.
“Now let’s be clear: this is not an amnesty,” Mr. Obama said in the Rose Garden, anticipating the Republican response. “This is not a path to citizenship. It is not a permanent fix.”
The group of illegal immigrants that will benefit from the policy is similar to those who would have been eligible to become legal permanent residents under the Dream Act, legislation that Mr. Obama has long supported. An effort by the White House to pass the bill in late 2010 was blocked by Republicans in the Senate. Mr. Obama called on Congress again Friday to pass that legislation.
The president was facing growing pressure from Latino leaders and Democrats who warned that because of his harsh immigration enforcement, his support was lagging among Latinos who could be crucial voters in his race for re-election.
Illegal immigrants said the new policy would make a major difference in their lives. As students, when they graduate from high school, they often cannot go on to college because they are not eligible for financial aid and must pay higher tuition rates. If they do succeed in graduating from college, regardless of their academic accomplishments, they cannot be legally employed in the United States or obtain driver’s or professional licenses.
Kirk Semple and Richard W. Stevenson contributed reporting.