A Democratic privacy advocate and libertarian-minded Republican are asking the nation's top intelligence official to release more information about the communications of American citizens swept up in surveillance operations.

The request by Democratic Sen. Ron Wyden of Oregon and GOP Sen. Rand Paul of Kentucky adds to a chorus of calls for more transparency about how intelligence agencies use and share communications to, from and about Americans.

The two want to know more about how agencies handle these communications as well as data about the number of Americans affected. They also want to make public the procedures on how intelligence about members of Congress is disseminated.

There are still "holes in the public's understanding of how U.S. person information — collected pursuant to different authorities and by different agencies — is handled," they wrote.

The senators' Friday letter to Dan Coats, director of national intelligence, comes as lawmakers gear up for debate over the reauthorization of one of the government's key surveillance programs, which expires at the end of the year. Programs authorized by Section 702 of the Foreign Intelligence Surveillance Act target foreigners, but domestic communications are sometimes vacuumed up as well. They were first revealed to the public by Edward Snowden, who leaked files from the National Security Agency.

Critics who want the law reformed worry that agencies use the foreign intelligence collection tool too loosely and sometimes in connection with domestic law enforcement investigations.

Intelligence officials have tried to allay concerns saying that any domestic communications collected are incidental to the targeting of foreigners.

They say Section 702 allows the government to target non-U.S. citizens reasonably believed to be located outside the United States and bars the government from targeting a foreigner to acquire the communications of an American or someone in the U.S. But they say intelligence agencies are authorized under Section 702 to query communications made with Americans in certain, approved cases.

Lawmakers seeking reforms could gain momentum from the investigation into Russian meddling in the presidential election. President Donald Trump recently made an unsubstantiated claim that his conversations were wiretapped. There also is controversy surrounding intercepts that revealed former national security adviser Mike Flynn's communications with the Russian ambassador.

The House intelligence committee probing Russian activities made a request for similar information earlier this year.

The House committee has scheduled a closed-door hearing for Tuesday with FBI Director James Comey and Adm. Mike Rogers, the head of the National Security Agency. That same day, former CIA Director John Brennan, former National Intelligence Director James Clapper and former Deputy Attorney General Sally Yates are to testify at an open hearing.