WASHINGTON — President Obama will ignore angry protests from Republicans and announce as soon as next week a broad overhaul of the nation’s immigration enforcement system that will protect up to five million unauthorized immigrants from the threat of deportation and provide many of them with work permits, according to administration officials who have direct knowledge of the plan.

Asserting his authority as president to enforce the nation’s laws with discretion, Mr. Obama intends to order changes that will significantly refocus the activities of the government’s 12,000 immigration agents. One key piece of the order, officials said, will allow many parents of children who are American citizens or legal residents to obtain legal work documents and no longer worry about being discovered, separated from their families and sent away.

That part of Mr. Obama’s plan alone could affect as many as 3.3 million people who have been living in the United States illegally for at least five years, according to an analysis by the Migration Policy Institute, an immigration research organization in Washington. But the White House is also considering a stricter policy that would limit the benefits to people who have lived in the country for at least 10 years, or about 2.5 million people.

Extending protections to more undocumented immigrants who came to the United States as children, and to their parents, could affect an additional one million or more if they are included in the final plan that the president announces. White House officials are also still debating whether to include protections for farm workers who have entered the country illegally but have been employed for years in the agriculture industry, a move that could affect hundreds of thousands of people.