WASHINGTON (AP) — The Obama administration maintains it is unable to say how many times one of the government's most politically sensitive anti-terrorism surveillance programs — which is up for renewal this week on Capitol Hill — has inadvertently gathered intelligence about U.S. citizens.

In a briefing for reporters on the 11th anniversary of the 9/11 terrorist attacks, the general counsel for the Office of the Director of National Intelligence said Tuesday that the program designed to monitor international communications by terrorist suspects has collected an extraordinary amount of valuable intelligence overseas about foreign terrorist suspects while simultaneously protecting civil liberties of Americans.

Originated by the George W. Bush administration, the program was publicly disclosed by The New York Times in 2005 and was restructured in 2008 to provide oversight by a secret federal court and with additional oversight from Congress.

Civil liberties groups and some members of Congress have expressed concern that the government may be reviewing the emails and phone calls of law-abiding Americans in the U.S. who are at the other end of communications with foreign terrorist suspects being monitored abroad.

The House began debating renewal of the program Tuesday and expected to vote Wednesday. A hold has been placed on the legislation in the Senate by one of the program's critics, Sen. Ron Wyden, D-Ore.

The program "is not a tool for spying on Americans," said Robert Litt, the general counsel for the Office of the Director of National Intelligence.

Litt said the program cannot be used to target American citizens and cannot be used to target people within the U.S. In addition, it cannot be used to collect the contents of any communication when all the participants are in the United States, said the ODNI's general counsel.

There has never been any intentional effort to bypass restrictions, he added.

At Tuesday's news briefing, reporters repeatedly pressed Litt on how many times there had been incidental collections of intelligence on Americans.

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Litt pointed out that the National Security Agency, the ODNI and independent inspectors general for each office have said information is not readily available on the number of instances involving unintentional monitoring of U.S. citizens.

Some members of Congress have suggested that the law contains a loophole that enables intelligence-gathering on U.S. citizens.

"I strongly take exception to the suggestion that there is a 'loophole,'" James Clapper, the director of national intelligence, said in a letter to 11 Senate Democrats and two Senate Republicans on Aug. 24.

The law prohibits "reverse targeting — targeting a person located outside the United States as a pretext when the real goal is to target a person inside the United States."

On Tuesday night, Sen. Mark Udall, D-Colo., said the DNI's Aug. 24 response does not sufficiently address Udall's concerns regarding "the possibility of unauthorized surveillance of Americans." Wyden criticized the lack of "even a ballpark estimate of how many Americans have had their communications collected under this law."

Asked at the news briefing about the program's successes, Litt said that the ability to collect certain kinds of communications that cannot be gathered any other way is "incredibly helpful." He said that being more specific would signal to the targets of the surveillance what was being collected.

In July, the administration acknowledged in a rare disclosure that the program had exceeded legal limits on at least one occasion, but that the problem had been remedied. The ODNI made the comment in a letter to Wyden, a member of the Senate Intelligence Committee.

On at least one occasion, the Foreign Intelligence Surveillance Court held that an intelligence collection effort was "unreasonable under the Fourth Amendment" requirement to obtain a court warrant, Wyden said at the time.

In response, the intelligence office said that Wyden's statements "may convey an incomplete and potentially misleading understanding" of what is at issue.

Litt said he had met with Wyden, talked through the issues and that the ODNI was prepared to continue doing that.

"If a problem develops, we fix it," Litt said of the program.