A senior government lawyer said Wednesday that the high volume of searches that the National Security Agency makes of a database that holds Americans’ and foreigners’ communications would make court approval for queries involving Americans impractical.

Appearing before the government’s civil liberties watchdog panel, Robert S. Litt, general counsel for the Office of the Director of National Intelligence, said “the number of times we query” the database for information “is considerably larger” than 288. That’s the number of queries made for a different type of data in a separate NSA program that Litt used as a comparison.

Requiring court sign-off for queries of Americans’ e-mails and phone calls had been the suggestion of a White House review panel on government surveillance activities as well as a number of lawmakers who are seeking changes to intelligence programs.

But Litt told the Privacy and Civil Liberties Oversight Board, an independent watchdog agency, that “the operational burden” would be so great that he suspects the Foreign Intelligence Surveillance Court, which oversees the program, “would be extremely unhappy if they were required to approve every such query.”

Replied board member and former federal judge Patricia Wald: “I suppose the ultimate question for us is whether or not the inconvenience to the agencies or even the unhappiness of the [surveillance] court would be the ultimate criteria.”

At issue is a 2008 law known as Section 702 of the FISA Amendments Act, which authorized the government to target foreigners reasonably believed to be located overseas. But officials say there are “minimization” rules to protect the privacy of Americans and there are reviews done to ensure that the agency is targeting foreigners.

NSA General Counsel Rajesh De said, for instance, that determining who is a foreigner is based on the “totality” of the circumstances and not on a percentage, as has been reported. “There is no 51 percent rule,” he said.

He also said that the communications that are collected “upstream” at the switches of telecommunications providers are held for only two years, in contrast to the five-year retention period for e-mails gathered from companies such as Google and Yahoo.

One reason for that shorter retention period, he said, is that the government makes a controversial type of query on the upstream communications in which they attempt to pluck out a foreign target’s e-mail address or phone number from the body of the communication, and not the “to” or “from” line.

The nature of the “about” queries — or queries about a target — means that “there is a greater likelihood of [picking up Americans’] communications or wholly domestic communications,” De said.

Those queries do not include general search terms, or even the person’s name, De said. They are made on the e-mail address or phone number, he said. Such queries are conducted only upstream and not at the e-mail companies, he said.

But experts who testified in a second panel said they did not believe that Congress intended to allow the government to make such queries. “To the contrary, when legislators discussed surveillance, they discussed surveillance of the target,” not “about” the target, said Jameel Jaffer, ACLU deputy legal director. “So I think this is an entirely foreign concept.”

In general, Jaffer argued, the agency’s “about” queries and the privacy and targeting procedures approved by the court exceed the law’s bounds.