In a stark concession to a new political reality in Washington, President Bush is abandoning the hotly debated surveillance program to intercept Al Qaeda communications to and from America without authorization from the courts.

Attorney General Gonzales said in a letter sent to Congress yesterday that the president’s decision was triggered by a ruling last week from the Foreign Intelligence Surveillance Court authorizing telephone and e-mail taps “where there is probable cause to believe that one of the communicants is a member or agent of Al Qaeda or an associated terrorist organization.”

Mr. Gonzales called the new court orders “innovative” and “complex,” and he said they obviated the need for the warrantless program that Mr. Bush authorized shortly after the terrorist attacks of September 11, 2001. “Accordingly, under these circumstances, the president has determined not to reauthorize the Terrorist Surveillance Program when the current authorization expires,” the attorney general said.

Democratic and Republican critics have been pressing Mr. Bush to submit the program to court review since it was disclosed by the New York Times in December 2005. Until yesterday, the administration publicly rejected those suggestions as impractical.

“It’s a total reversal,” a law professor opposed to the warrantless surveillance scheme, David Cole of Georgetown University, said. “Here you have a commander in chief contending he can ignore congressional statute and spy on Americans without court approval. Now, suddenly, he faces a Democratic Congress … and says, ‘I will abide by the law.'”

Mr. Gonzales said yesterday that administration lawyers have been considering a court-sanctioned substitute for the surveillance program since the spring of 2005. He also said it took “considerable time” for the judge handling the recently approved application to make the ruling.

However, the timing of the announcement of the warrantless program’s termination seemed intended to calm the political waters. It came in a letter to the chairman and ranking member of the Senate Judiciary Committee just hours before Mr. Gonzales was scheduled to go before that panel for its first oversight hearing since the Democrats took power.

The Justice Department yesterday stood by its claims that the surveillance program was legal under the president’s constitutional authority and under Congress’s 2001 resolution authorizing the use of military force against America’s attackers. However, the decision to bring the program within the constraints of the Foreign Intelligence Surveillance Act of 1978 has several potential benefits for the administration.

While the surveillance done under the president’s unilateral program was of untested legal value in criminal cases and had complicated some prosecutions, wiretaps done within the 1978 law are regularly admissible in court. “There is well established authorities and patterns for the use of information obtained through FISA surveillance,” a senior Justice Department official said, speaking on condition of anonymity.

In addition, the explicit legalization of the program could defuse some of the various lawsuits challenging it. In August, a federal judge in Detroit, Anna Diggs Taylor, declared the program unconstitutional. The Justice Department is appealing that ruling. Yesterday, government lawyers filed Mr. Gonzales’s letter with the court, though they did not indicate whether they will now argue that the case is moot.

Mr. Cole said the government’s move will have a limited impact on the litigation. “It may narrow the lawsuits. It doesn’t necessarily eliminate them,” he said.

In a written statement, the new Judiciary Committee chairman, Senator Leahy of Vermont, welcomed Mr. Bush’s decision, but in a floor speech, he railed against the administration for adopting the surveillance program in the first place.

“They don’t have to follow the law. They just step outside the law. They don’t have to follow the checks and balances,” Mr. Leahy said. “No matter what your political leanings might be, all Americans ought to ask, ‘Why are they doing this?’ … In the long run, it does not protect us, not if we take away our liberties.”

The ranking member of the Judiciary Committee, Senator Specter of Pennsylvania, who declared the warrantless tapping program flatly illegal after it was disclosed in 2005, said the Congress needs more information about the administration’s change of heart.

“There needs to be oversight beyond what has been disclosed in this letter. But at least there is a very significant first step,” he said in a floor speech. “It is regrettable that these steps weren’t taken a long time ago. I’d like to have an explanation … when there has been such a public furor and public concern.”