(CNN) - National Security Agency chief Gen. Keith Alexander, in response to a letter from Sen. Bernie Sanders, said Tuesday that nothing the agency does "can fairly be characterized as 'spying on Members of Congress or American elected officials.'"

Alexander did not offer any further details about members of Congress specifically, arguing that doing so would require him to violate the civilian protections incorporated into the surveillance programs.

"Among those protections is the condition that NSA can query the metadata only based on phone numbers reasonably suspected to be associated with specific foreign terrorist groups," Alexander wrote.Sanders, I-Vermont, had written to Alexander earlier this month asking whether the NSA is currently spying "on members of Congress or other American elected officials" or had in the past.

An NSA spokesperson gave a general response to the inquiry at the time, saying that "members of Congress have the same privacy protections as all U.S. persons" and that they were reviewing the senator's letter.

Alexander's letter, which was personally addressed to Sanders, was more specific.

Sanders has publicly questioned the legality of the NSA surveillance programs recently, calling them "a clear violation of the Fourth Amendment ban on unreasonable searches."

When asked about the balance between civilian privacy and counterterrorism surveillance earlier this month, Sanders told CNN: "We have to be vigorous in protecting the American people from terrorism. But I very strongly believe we can do that in the context of the U.S. Constitution. I believe what the NSA is doing now is not constitutional."

The push back against the possible surveillance practices of the NSA has created unlikely bedfellows in the Senate, with tea party favorite Sen. Ted Cruz, R-Texas, suggesting the methods of data collection have "not been effective enough monitoring and surveilling bad guys" but rather "too broad with respect to law-abiding citizens."

Cruz added that the NSA's response to Sanders' question of whether members of Congress have had phone records or other data monitored "suggests the answer to that question was in the affirmative."

The NSA has been the subject of scrutiny since former agency contractor Edward Snowden released extensive classified documents on various domestic surveillance programs last year.

For his part, Sanders has introduced legislation that would prohibit the collection of phone records without a warrant, although it is unlikely such a law would make any progress in Congress.