WASHINGTON — President Bush personally blocked a Justice Department investigation of the anti-terror eavesdropping program that intercepts Americans’ international calls and e-mails, administration officials said yesterday.

Mr. Bush refused to grant security clearances for department investigators who were looking into the role Justice lawyers played in crafting the program, under which the National Security Agency listens in on telephone calls and reads e-mail without court approval, Attorney General Alberto Gonzales told the Senate Judiciary Committee.

Without access to the sensitive program, the department’s Office of Professional Responsibility closed its investigation in April.

“It was highly classified, very important and many other lawyers had access. Why not OPR?” Senator Specter, a Republican of Pennsylvania, the committee chairman, asked Mr. Gonzales.

“The president of the United States makes the decision,” Mr. Gonzales replied.

Later, at the White House, spokesman Tony Snow said the eavesdropping program is reviewed every 45 days by senior officials, including Mr. Gonzales. The president did not consider the Justice unit that functions as a legal ethics watchdog to be the “proper venue,” Mr. Snow said.

“What he was saying is that in the case of a highly classified program, you need to keep the number of people exposed to it tight for reasons of national security, and that’s what he did,” Mr. Snow said.

Yet, according to OPR chief Marshall Jarrett, “a large team” of prosecutors and FBI agents were granted security clearances to pursue an investigation into leaks of information that resulted in the program’s disclosure in December. The Justice Department inspector general, Glenn Fine, and two of his aides were among other department officials who were granted clearances, Mr. Jarrett said in an April memo explaining the end of his probe. That memo was released by the Justice Department yesterday.

The existence of the eavesdropping program outraged Democrats, civil libertarians, and even some Republicans who said Mr. Bush overstepped his authority.

A group of 13 prominent legal experts wrote lawmakers last week that the Supreme Court’s recent decision striking down military commissions for detainees at the Guantanamo naval base in Cuba “strongly supports the conclusion that the president’s NSA surveillance program is illegal.”

Rep. Maurice Hinchey, a Democrat of New York who requested the Justice Department investigation, said he and other lawmakers were preparing a letter to Mr. Bush asking him to allow the probe to go forward. “We can’t have a president acting in a dictatorial fashion,” Mr. Hinchey said.

Mr. Gonzales insisted yesterday that the president “has the inherent authority under the Constitution to engage in electronic surveillance without a warrant.”

Still last week, under a deal with Mr. Specter, Mr. Bush agreed conditionally to a court review of the warrantless eavesdropping operations.

Mr. Bush’s 2001 directive authorized the National Security Agency to monitor — without court warrants — the international communications of people on American soil when terrorism is suspected. The administration initially resisted efforts to write a new law, contending that no legal changes were needed. But after months of pressure, officials have grown more open to legislation.

Under the deal with Mr. Specter, the president agreed to support a bill that could submit the program to the secretive Foreign Intelligence Surveillance Court for a constitutional review.

Last week, Mr. Gonzales said the bill gives Mr. Bush the option of submitting the NSA program to the intelligence court, rather than requiring the review. Mr. Specter said yesterday that Mr. Bush assured him he will seek the court review if the legislation passes without significant amendment.