Prism and Upstream, two surveillance programs first revealed by former National Security Agency (NSA) contractor Edward Snowden, are set to expire at the end of the year. However, intelligence agencies have continued not to disclose to Congress how many Americans have had communications caught up in the spying efforts.

Upstream and Prism operate under Section 702 of the Foreign Intelligence Surveillance Act, which allows intelligence agencies to acquire foreign intelligence information concerning people who aren’t citizens of the United States and are located outside the country.

Prism is used to collect messaging data from major tech companies including Apple, Google, Facebook, Microsoft that is sent and received by foreign targets under surveillance. Upstream gives the NSA the ability to intercept internet traffic flowing along the "internet backbone"—major Internet cables and switches—located in the U.S. and overseas.

Read: WikiLeaks: CIA Hacked Phones And TVs To Turn Them Into Spy Devices

That section of the law is set to expire at the end of the year on Dec. 31. The White House reportedly supports the renewal of the law as-is and is not pushing for reforms to the programs despite widespread criticism of the wide net they cast.

Congress has started to process of renewal, reviewing the law and its effects, but has continually had a request denied to learn how many Americans have their electronic communications intercepted by the programs.

Democratic Congressman John Conyers of Michigan, a member of the House Judiciary Committee, is the latest to ask for figures from the intelligence community. Last week, he informed a panel hearing that Congress would need to know the numbers to help decide on reauthorization.

"The members of this committee and the public at large require that estimate to engage in a meaningful debate," he said.

Read: How Much Does The Government Spy On Us? US Officials To Announce Extent Of Surveillance

Conyers is joined in his request by Democratic Senator Ron Wyden from Oregon, a member of the Senate Intelligence Committee. Wyden has pressed the director of national intelligence for the information in 2011, 2012 and 2014, and has renewed his request in a letter sent to Daniel Coats, the Trump administration’s choice for director of national intelligence.

"I and other members of Congress have been seeking an answer to this question since 2011. We posed the question again in the context of the reauthorization of Section 702. It is now central to the debate this year over the reauthorization of the program, which you have described as your 'top legislative priority,” Wyden wrote.

Coats reportedly told Wyden he would "do everything I can" to "get you that number," but provided no guarantee that he would follow through.

According to April Doss, a former NSA lawyer who testified before the House Judiciary Committee earlier this month, U.S. spies don’t keep track of the number of American citizens caught by the surveillance programs because doing so would create its own privacy concern.

She reasoned that identifying whether a person caught in the spy net would require spies to de-anonymize data collected, including phone numbers and IP addresses, to determine whether the person attached to that data is an American.

Doss said that practice would “constitute an unnecessary and unwarranted intrusion on the privacy of U.S. persons” and would also likely be illegal as it would be “both intrusive and unrelated to any need for foreign intelligence gathering.”

Privacy organizations like the Electronic Frontier Foundation have called on Congress to put an end to the programs by letting them expire at year’s end.

“We've long argued that the surveillance programs under Section 702 are not targeted, do not have sufficient oversight, and violate Fourth Amendment protections. That's why we’re calling on Congress to let the authority sunset," the EFF’s Kate Tummarello wrote in a blog post earlier this month.