The National Security Agency may shut down a controversial program that vacuums up hundreds of millions of call and text message records.

A senior Republican aide who appeared on a Lawfare blog podcast said the Trump administration had let the program stagnate in recent months and was considering ending it altogether. The comments were first noted by The New York Times.

the program allows surveillance of Americans

The program, which was disclosed by Edward Snowden, became a focus of privacy activist ire after it was revealed. Under the system, the NSA can obtain call log data not only on foreign surveillance targets, but also on Americans. Intelligence officials have repeatedly said that the work is crucial to national security, but civil rights advocates have been skeptical.

The controversy over the program eventually led to the passage of the USA Freedom Act, which curbed some of the agency’s spying powers. At the end of the year, the legal authority underpinning the program is set to expire, which the White House might not look to renew.

As recently as last year, the program was still causing controversy. The NSA said at the time that it would delete a massive database of records after inadvertently gathering more data than it was authorized to receive.