Reid has been urging swift passage of the legislation, which lets the FDA charge drug companies user fees when they submit their brand name drugs for approval.

Earlier on Monday Reid said he was "cautiously optimistic" about the legislation's likely passage. He, as well as, Sens. Mike EnziMichael (Mike) Bradley EnziGOP is addressing tax cuts and a pension bill that could help coal miners Overnight Finance: Congress sends Trump funding bill to avert shutdown | WH sees 'tentative' deal on defense spending | GOP discovers corporate tax snag | Consumer bureau fight heats up | Apple could see B windfall from tax bill Overnight Finance: Congress sends Trump bill to avert shutdown | GOP discovers corporate tax snag | CFPB leadership battle rages MORE (R-Wyo.) and Tom HarkinThomas (Tom) Richard HarkinOrrin Hatch, ‘a tough old bird,’ got a lot done in the Senate Democrats are all talk when it comes to DC statehood The Hill's 12:30 Report MORE (D-Iowa), the cosponsors of the bill, have said they hope the bill does not change too much going forward given the bipartisan support it has in its current form.

"I'm cautiously optimistic that the spirit of bipartisanship will continue because Democrats can't pass this legislation without the cooperation of our Republican colleagues," Reid said.

Later on Monday Harkin said he expected the Senate to vote on amendments to the legislation as the chamber has with other recent bills. Harkin said he hopes those amendments would be relevant to the FDA bill.

"I would say neither Democrats nor Republicans got everything they wanted in this bill," Harkin said. "We would expect that all of these amendments would be relevant to the bill."