The Obama administration, anticipating that Congress might not pass comprehensive immigration reform this year, is considering ways it could act without congressional approval to achieve many of the objectives of the initiative, including giving permanent resident status, or green cards, to large numbers of people in the country illegally.

The ideas were outlined in an unusually frank draft memo prepared for Alejandro N. Mayorkas, director of the federal agency that handles immigration benefits, U.S. Citizen and Immigration Services (USCIS). The memo lists ways the government could grant permanent resident status to tens of thousands of people and delay the deportation of others, potentially indefinitely.

"In the absence of Comprehensive Immigration Reform, CIS can extend benefits and/or protections to many individuals and groups by issuing new guidance and regulations," said the memo, which was prepared by four senior officials from different branches of USCIS.

The 11-page document was made public Thursday by Sen. Chuck Grassley, R-Iowa, who with six other senators wrote to Obama more than a month ago, asking for his assurance that rumors that some sort of reprieve was in the works for millions of illegal immigrants weren't true.

"The administration has failed to reassure us that the information we were hearing was inaccurate," Grassley said in a statement to ProPublica Thursday night. "This memo gives credence to our concerns that the administration will go to great lengths to circumvent Congress and unilaterally execute a back door amnesty plan."

The memo's release is certain to put the administration on the defensive with opponents of "comprehensive immigration reform" -- Washington code for putting many of the estimated 12 million people in the country illegally on a potential path to citizenship. It is also likely to make immigration an even hotter topic in this year's congressional elections, which have already been roiled by Arizona's controversial attempt to use state and local police to enforce federal immigration laws.

Christopher Bentley, a USCIS spokesman, said last night that the agency would not comment on details of the memo, which he described as an internal draft that "should not be equated with official action or policy of the Department...We continue to maintain that comprehensive bipartisan legislation, coupled with smart, effective enforcement, is the only solution to our nation's immigration challenges."

Bentley said that internal memos help the agency "do the thinking that leads to important changes; some of them are adopted and others are rejected" and that "nobody should mistake deliberation and exchange of ideas for final decisions."

"To be clear," he said in an e-mail, the Obama administration "will not grant deferred action or humanitarian parole to the nation's entire illegal immigrant population."

One of the memo's most controversial suggestions is wider use of "deferred action," the agency's discretion to indefinitely delay the deportation of otherwise deportable non-citizens. "This would permit individuals for whom relief may become available in the future to live and work in the U.S. without fear of removal," the memo said.

The memo acknowledges that granting deferred action to an unrestricted number of people "would likely be controversial, not to mention expensive." Instead, it suggests that this option be used for particular groups, such as the approximately 50,000 young people who would be allowed to stay in the country if Congress passed the Dream Act. That bill would provide a potential path to citizenship for qualifying young people who complete a college degree or two years of military service.

The memo also says that standards for "extreme hardship" cases could be eased so "many more spouses, sons and daughters of U.S. citizens and lawful permanent residents" could seek relief without fearing deportation.

In what would be a reversal of a position held by the agency's Office of General Counsel under previous administrations, the memo suggests granting green cards to large numbers of people currently in the country under Temporary Protected Status. That status typically is used to forestall deportation proceedings for large groups of undocumented foreign nationals when it would cause them hardship, such as sending them home in the wake of a major earthquake or hurricane or during a civil war.

Supporters of comprehensive immigration reform are certain to welcome any effort by the Obama administration to unilaterally open pathways to citizenship for many currently in the country illegally. But the draft is also sure to outrage immigration-restriction groups.

"The memo proposes 18 different ways for the Obama administration to essentially eliminate our borders through regulatory fiat and in clear violation of the letter and the spirit of U.S. immigration laws, which Obama swore an oath to faithfully execute," said Rosemary Jenks, director of government relations for NumbersUSA, an organization that lobbies for tighter immigration laws and practices.