Hopes that Senate lawmakers would act quickly to pass spending bills and reduce the odds of a shutdown this fall were dashed this week, as appropriators immediately ran into roadblocks when they started the process to set line-by-line funding for agencies across government.

The Senate Appropriations Committee canceled a series of markups this week—both preliminary votes at the subcommittee level and final approval before the full panel scheduled for Thursday—over a dispute on which policy riders would be attached to the funding measures. Senate leaders in both parties subsequently raised concerns about the chamber’s capacity to work quickly to approve the required spending bills, with each pointing fingers at the other side for engaging in overtly political maneuverings. Current funding for agencies across government lasts through Sept. 30.

At issue is a handshake agreement to avoid “poison pill” add-ons to appropriations bills. The agreement was struck as part of the bipartisan budget deal President Trump signed into law earlier this summer to set the top-line spending levels. Lawmakers said the agreement would avoid thorny issues, such as abortion and blocking the Trump administration from shifting funds to pay for barriers along the U.S.-Mexico border. Washington Democratic Sen. Patty Murray said, however, that she planned to introduce an amendment to block the administration’s rule that restricted Title X family planning grant recipients from discussing abortion with patients, and the committee declined to move forward with a vote until lawmakers sorted out how to proceed with riders.

Senate Majority Leader Mitch McConnell, R-Ky., said on Wednesday that Democrats were failing to uphold their end of the bargain.

“With only a few weeks to go until the end of September, we have no time to waste when it comes to appropriations,” McConnell said from the Senate floor. “Everyone on both sides agreed there would be no poison pills, no partisan wrenches thrown into the gears. Unfortunately, yesterday brought some disturbing signals that Democrats may be rethinking that commitment.”

Senate Minority Leader Chuck Schumer, D-N.Y., similarly sounded the alarm on the lack of progress, but blamed Republicans for setting the top-line spending level for each of the 12 annual appropriations bills without consulting Democrats. He also condemned a proposal to add $12 billion for border wall funding.

“Already we're running into trouble with those allocations this time around,” Schumer said Wednesday morning. “Step one in the appropriations process and the spirit of bipartisanship necessary for this work might be, might be melting away.”

He added Republicans “know very well this will not fly with Senate Democrats." The Democrats are “not going to vote for a budget that is partisan, attempted to be jammed down our throats that puts an additional $12 billion in the wall," he explained. "Forget that.”

The House has passed most of the required annual spending bills for fiscal 2020, but lawmakers still must reconcile them with the Senate, which has yet to approve any appropriations bills for the upcoming fiscal year. The upper chamber delayed work on the spending bills until top-line funding levels were established under the budget deal that Trump has signed into law. A Senate subcommittee on Tuesday approved a Defense Department spending bill for fiscal 2020. The full panel is set to approve that bill on Thursday, but has delayed scheduled votes on two bills to fund the departments of Labor, Health and Human Services, and State, as well as other agencies.

Despite the early hiccups, both sides remained cautiously optimistic they could put their differences aside and avoid another government shutdown. Both McConnell and Schumer acknowledged a continuing resolution would likely be necessary to avoid a shutdown in October, which House leaders have already called unavoidable.

“I maintain hope that [Appropriations Committee leaders] can oversee a smooth process, that we can move all 12 appropriation bills in a bipartisan fashion,” McConnell said. “Both sides have every reason to want a smooth appropriations process to proceed as we have planned. I hope that's exactly what happens in committee this week and on the floor soon thereafter.”

Schumer said there is “still time to get this back on track.”

“Certainly our side wants to avoid a Republican shutdown and we hope our Republican colleagues will have the good sense not to let President Trump lead them into that cul-de-sac once again,” he said. “So let's sit down and make this work.”