Sen. Ron WydenRon WydenMnuchin aiming for tax reform by August Dems rip Trump administration for revoking Obama's transgender directive IPAB’s Medicare cuts will threaten seniors’ access to care MORE (D-Ore.) on Thursday said Congress should require intelligence agencies to provide estimates of how often the emails and phone calls of Americans are collected during the surveillance of terrorist suspects overseas.

Wyden opened debate on the Foreign Intelligence Surveillance Act (FISA) Amendments Reauthorization Act, H.R. 5949, on Thursday morning, and the Senate could hold a vote on it this week. The bill would extend for five years the ability of U.S. intelligence authorities to surveil terrorists overseas without first getting permission from a court.

Wyden said he supports the goals of FISA, but said his amendment to the bill is needed because intelligence officials have been unable to provide any details on how often American communications are picked up during surveillance. He said he and other senators have asked the director of national intelligence for that information, but have received little in the way of a response.

"The response was … 'It is not reasonably possible to identify the number of people located in the United States whose communications may have been reviewed under the authority of the FISA amendments act,' " Wyden said.

Last July, Wyden and a dozen other senators asked for an estimate — whether there were thousands or millions of American communications being captured in the course of conducting overseas surveillance — but again received no meaningful respone.

"I think, when you talk about oversight, and you can't even get a rough estimate of how many law-abiding Americans had their communications swept up by this law … the idea of robust oversight, really ought to be called toothless oversight if you don't have that kind of information," he said.

The senator has pressed for information about whether any communications between two U.S.-based people have been accidentally swept up in the surveillance programs — again to no response, according to Wyden.

"So if you're looking for reassurance that the law is being carried out in a way that respects the privacy of law-abiding American citizens, you won't find it in his response."

Wyden's amendment is one of three that could receive a vote as early as this week. His language would require the director of national intelligence to report to Congress on any estimate on the number of U.S.-based communications that have been picked up in the process of conducting overseas surveillance, and whether any wholly domestic U.S. communications have been part of it.

It also requires intelligence officials to determine whether any intelligence agency has tried to search through these collected communications for any relating to an American citizen without first obtaining a warrant.

Wyden's amendment is one of three that could be considered in the coming days and weeks. Another from Sen. Jeff MerkleyJeff MerkleyPoll: Senate should confirm Gorsuch A guide to the committees: Senate Senate advances Trump's Commerce pick MORE (D-Ore.) would require FISA court opinions to be declassified.

Today, FISA opinions remain classified, which Wyden said prevents people from understanding the surveillance law at all. He said that, while portions of these court decisions should be redacted, the law itself "should not be a secret."

A second amendment is from Sen. Rand PaulRand PaulConquering Trump returns to conservative summit Rand Paul rejects label of 'Trump's most loyal stooge' GOP healthcare plans push health savings account expansion MORE (R-Ky.), which is expected to clarify that the Fourth Amendment to the Constitution protects U.S. citizens from unreasonable searches and seizures, even those that result from searches being done by a U.S. intelligence agency monitoring a foreign national overseas.