by James Risen and Eric Lichtblau

WASHINGTON - President-elect Barack Obama [1] will face a series of early decisions on domestic spying that will test his administration's views on presidential power and civil liberties.

The Justice Department will be asked to respond to motions in legal challenges to the National Security Agency [2]'s wiretapping program, and must decide whether to continue the tactics used by the Bush administration - which has used broad claims of national security and "state secrets" to try to derail the challenges - or instead agree to disclose publicly more information about how the program was run.

When he takes office, Mr. Obama will inherit greater power in domestic spying power than any other new president in more than 30 years, but he may find himself in an awkward position as he weighs how to wield it. As a presidential candidate, he condemned the N.S.A. operation as illegal, and threatened to filibuster a bill that would grant the government expanded surveillance powers and provide immunity to phone companies that helped in the Bush administration's program of wiretapping without warrants. But Mr. Obama switched positions and ultimately supported the measure in the Senate, angering liberal supporters who accused him of bowing to pressure from the right.

Advisers to Mr. Obama appear divided over whether he should push forcefully to investigate the operations of the wiretapping program, which was run in secret from September 2001 until December 2005.

Mr. Obama recently started receiving classified briefings on intelligence operations from Mike McConnell [3], the director of national intelligence. The Obama transition team [4] declined to say whether Mr. Obama had been briefed on the agency's eavesdropping operations.

His transition team also declined requests to discuss his current views on domestic surveillance or how his administration would respond to legal challenges growing out of it. But there has been no shortage of debate among lawyers involved in the challenges to the program.

"I don't think President-elect Obama embraces Dick Cheney [5]'s theory of unfettered presidential power," said Jon B. Eisenberg, a San Francisco lawyer involved in one lawsuit against the wiretapping program. "So if President-elect Obama doesn't embrace that theory, one would expect a change in the direction of how the new administration handles this litigation."

But other legal and political analysts suggest that Mr. Obama, as president, may be more willing to accept the broadened presidential powers that he once condemned as a candidate, particularly since Congress has approved expanded surveillance powers for the government.

In the proposal in June that Mr. Obama ultimately voted to support, Congress set up a new surveillance framework that gave intelligence officials much broader authority to eavesdrop on international communications without prior court approval.

One of the first clues of how the Obama administration will deal with the issue of domestic surveillance may come in a court case in Alexandria, Va., where a judge has ordered the Justice Department to turn over material from the National Security Agency and other intelligence agencies on possible eavesdropping on Ali al-Timimi, an Islamic leader convicted of supporting terrorism. The Justice Department has never acknowledged that it has used intercepts from the N.S.A. program in any criminal or civil case, which could be unlawful because the wiretaps were conducted without court warrants.

Mr. Timimi has claimed that he did not get a fair trial because prosecutors secretly used N.S.A. wiretaps in his case, and he also argues that the government has turned over to the court only intercepted conversations that make him look guilty, while withholding those that might prove he is innocent. A recently unsealed transcript, citing a closed hearing, strongly suggests that the wiretaps were used in Mr. Timimi's criminal trial.

"We believe that the undisclosed interceptions already uncovered in this case are serious and knowing violations of federal law," said Jonathan Turley, a lawyer for Mr. Timimi.

Meanwhile, an Islamic charity in Oregon that had its assets frozen by the Treasury Department on the ground that it was also supporting terrorism is pushing ahead with a lawsuit of its own. The Obama administration must decide whether to continue to use the state-secrets privilege in order to block the disclosure of information about any N.S.A. eavesdropping.

The charity, Al-Haramain Islamic Foundation, is charging, based in part on a classified document that the government mistakenly gave to its lawyers, that it was the target of wiretapping without warrants. Lawyers for the group say they believe that the N.S.A. listened illegally not only to the international phone calls of members of the charity itself, but also to the calls of two of its lawyers in Washington.

Mr. Eisenberg, a lawyer for Al-Haramain, said the Justice Department had frustrated efforts to develop evidence in the case both by invoking the state-secrets claim and by refusing to grant security clearances to some members of the charity's legal team.

"In every way, they've stonewalled us, and the new administration can change all that," Mr. Eisenberg said. "They can take the blindfolds off."

In perhaps the most critical test, civil liberties groups that are suing major phone companies that took part in the N.S.A. program are waiting to find out whether a federal judge will throw out the lawsuits based on immunity granted by Congress in June.

The Justice Department has already moved to take advantage of the immunity provision by certifying in court that the phone companies were complying with a presidential order. But the Electronic Frontier Foundation, a civil liberties group that has taken the lead in the lawsuit, maintains that Congress acted beyond its powers.

A hearing is set for Dec. 2. Cindy Cohn, legal director for the foundation, said that as the case moved forward the new administration could act to withdraw the immunity certification made by the Bush Justice Department.

"Nothing will be over by Jan. 20," when Mr. Obama is inaugurated, Ms. Cohn said.

The Obama Justice Department will inherit the litigation in all of those cases, and some of the defense lawyers involved in the cases may try to force legal action that could tip the hand of the new administration.

Mr. Timimi's lawyers may soon file a new challenge, ensuring that a new attorney general would have to decide almost immediately on taking office how to respond.

But at least one Obama legal adviser said that new administrations often faced complex decisions on whether to change course in the middle of continuing legal matters.

"It's not always an easy thing for the office of legal counsel or the solicitor general on when to change a position," said Laurence H. Tribe [6], a professor at Harvard Law School who taught Mr. Obama when he was a law student there.

Another early decision facing the administration will be whether to work with the Democratic-controlled Congress to investigate the Bush administration officials who approved and ran the wiretapping program. While Congress gave the telecommunications companies legal immunity, it did not extend immunity to administration officials.

Some Democratic lawmakers have said they would like to conduct a more thorough investigation than was possible during Mr. Bush's tenure, but other Democratic advisers say they see little gain from trying to investigate past abuses and that an investigation risks harming the bipartisan spirit of cooperation that Mr. Obama has promised.

Since the election, Mr. Obama has not said whether his administration would engage in such inquiries of his predecessor's government.

But Mr. Obama was one of only 15 senators who voted against the confirmation of Michael V. Hayden [7] as director of the Central Intelligence Agency [8] in May 2006, largely because of Mr. Hayden's role as director of the N.S.A. when the wiretapping program was begun. At the time, Mr. Obama called Mr. Hayden a "troublesome choice" for C.I.A. director, and said he was "voting against Mr. Hayden in the hope that he will be more humble before the great weight of responsibility that he has not only to protect our lives but to protect our democracy."

During the general election campaign, Mr. Obama's aides offered cautious statements about whether he believed any investigations of past administration actions would be appropriate.

In an interview last summer, Gregory B. Craig [9], who is Mr. Obama's pick for White House counsel, said that Mr. Obama believed that Mr. Bush had abused his power by authorizing wiretapping without warrants. "The idea that the president can do almost anything that he deems necessary in the name of his war powers or national security, there is nothing in the Constitution that supports that, and it goes against 200 years of Supreme Court [10] jurisprudence," Mr. Craig said.

Some senior Democratic lawmakers are reluctant to comment now on whether they will pursue investigations of the wiretapping program or other Bush administration actions.

Senator Sheldon Whitehouse, Democrat of Rhode Island and a former federal prosecutor who now sits on the Judiciary and Intelligence committees, responded cautiously Friday when asked whether the Senate might investigate the program.

"I expect Congress will work with the Obama administration to assure the American people that their government will not go down this unlawful path again," Mr. Whitehouse said, adding that he was awaiting the results of an investigation of the N.S.A. program by the Justice Department inspector general and ethics office.