"Everything's a little up in the (air)," Sen. John Cornyn of Texas, a member of the Republican leadership told reporters crowded outside his office waiting for word of an agreement. "Hope springs eternal."
With no deal at hand, Senate leaders delayed until at least Tuesday a procedural vote to begin debate on the bill in hopes it might be ready then.
In one sign of possible progress late Monday, Sen. Chuck Schumer of New York, who is a member of the Democratic leadership, told reporters that negotiators had resolved a key sticking point over language in the Zika measure that would prevent funds from going to a Planned Parenthood partner in Puerto Rico, something Democrats strongly oppose.
"Yes, it's resolved," Schumer told reporters. "The whole Zika issue has been resolved."
But a top Senate GOP leadership aide declined to confirm Schumer's pronouncement. And about an hour before Schumer spoke, Sen. Roy Blunt of Missouri, a senior Republican in the talks, said it would be "very, very premature" for Democrats to say the Zika language had been resolved.
"None of this done until it's all done," Blunt said.
Some senators and aides of both parties predicted a hand-shake agreement on the overall deal could be reached as early as Tuesday but others doubted the partisan divide could be bridged so quickly, especially since the deadline for the government to run out of money is not until the end of the month.
With control of the Senate up for grabs in November, GOP leaders are anxious to wrap up the high-priority legislation and get their vulnerable members up for re-election home to campaign. Democrats denied Republican charges they were slow-walking a final agreement but privately acknowledged that they felt no pressure to accept a quick deal they didn't like just to let Republicans go home to campaign.
Among the issues being negotiated, Sen. Ted Cruz, R-Texas, is pushing to add language to the government funding bill that would prevent the US from turning over to an international organization control over Internet domain names. Some Democrats are pressing for changes to the Export-Import Bank board to get around GOP opposition to confirming open slots on the board, which is disrupting some operations of the bank.
Other issues include funding for Flint, Michigan's water supply problem, disaster aid for states hit my major flooding, disclosure requirements for political giving by corporations, and the number of hours truckers are allowed to drive in a week to limit driver fatigue.
Some GOP lawmakers have been pushing for aid to help with damage caused by the recent Louisiana flooding.
But Schumer suggested that both Flint and Louisiana would need to be addressed in a separate disaster aid package, saying the GOP was blocking additional money for Flint in the government funding package.
"They want to do Louisiana, we want to do Flint," Schumer said. "They don't want to do Flint."
Negotiators are also working to get offsets for the cost of the $1.1 billion Zika funding. Democrats initially pressed for it all to be considered emergency funding but there were signs they were prepared to meet GOP demands for some offsets.