Lawmakers in Congress are staring at the real possibility that a key law allowing the U.S. to gather the communications of foreign threats abroad will expire.

They say that if Section 702 of the Foreign Intelligence Surveillance Act, or FISA, lapses, it would be happening at a particularly vulnerable time, given the U.S.’s ongoing war in Iran. And they say it could create a blind spot regarding crucial data.

“If we lose FISA, we lose the ability to defend this country the way that it should be defended,” said Sen. Mike Rounds, a member of the Senate Armed Services and Intelligence committees. “We use that information to find out what the bad guys are doing, where they’re at, what they’re looking to attack, what their strategies are.”

“We really need them to take a look at the other side of this, which is, are you going to hurt Americans?” Rounds said of the holdouts. “Are you going to put Americans in harm’s way because you can’t come to a decision on how to make sure that this particular product stays available for the men and women who are defending our country?”

FISA provides the legal authority for federal agencies to collect and search the data of potential foreign threats.

But for months lawmakers have been unable to come to a deal on how to extend it because many Democrats don’t trust the Trump administration enough to give the program a clean extension, and conservative hard-liners want privacy guardrails added. That’s left Republican leadership without a coalition to pass a meaningful extension.

The surveillance can continue even if Congress fails to act because a court recertified 702 in September. But because of a quirk in the law, telecommunications companies, which usually provide much of that data to the U.S. government, would likely stop providing it for fear of getting sued.

“They’re going to be reluctant, I think, to proceed in cooperation with the government under a very unclear authority,” said Emily Harding, vice president of the Defense and Security Department at the Center for Strategic and International Studies.

“So either the authority expires, and then suddenly we lose a big stream of collection while all these legal battles go on, or the companies just kind of decide they’re going to keep working with the government and risk it, which I find slightly less likely.”

Losing that data could create a blind spot, Harding said, for potential spying on Iran, or predicting cyberattacks in advance.

“If you had suddenly the [telecommunications companies] not wanting to further participate, you’re taking away one of the most important tools we have against terrorist threats and a host of other threats,” said Sen. Mark Warner, the top Democrat on the Intelligence Committee.

After negotiations fell apart earlier in April, Congress passed a 10-day extension to allow time to continue negotiating. But a week later, members of the House — where the bulk of the debate is playing out — have little progress to show for it.

“They should pass what we said, like two weeks ago, and save a bunch of damn time, and pass a 60-day extension,” Rep. Chip Roy, who wants a warrant requirement and other privacy safeguards added to the law, told reporters Tuesday. “It wouldn’t be that hard. And then let’s all sit down and figure out how to make the reforms that are necessary.”

Now that the new deadline is rapidly approaching with no guarantee of passing a deal on the floor, lawmakers on both sides of the Capitol are grappling with what a lapse in the program would mean.

“I want to keep the country safe. If something happens, I don’t want that,” said Rep. Ralph Norman, a Republican who is still pushing for reforms.

Joe Gould contributed to this report.