Senate Democrats hit pause on a government funding bill on Wednesday night after Senate Minority Leader Mitch McConnell (R-KY) demanded a vote on an amendment targeting the Obama administration’s new rules to combat climate change.

Senate Appropriations Chair Barbara Mikulski (D-MD) pulled consideration of the energy and water bill — one of various measures to avert a government shutdown on Oct. 1 — after the top Senate Republican offered his amendment to prevent funding for the implementation of the Environmental Protection Agency’s rules on coal-fired power plants until the administration certified that it wouldn’t harm jobs or raise utility rates.

The move creates a new wrinkle in the GOP’s push to use government funding legislation to block the President Barack Obama’s rules on coal, potentially at the risk of a shutdown. It appears Senate Democratic leaders are worried that the McConnell amendment might pass — or at least put their vulnerable red-state members in a tough spot.

“Last night, the Senate Democrat leadership pulled the energy and water bill from consideration – for one reason: to protect the Administration’s new job-killing coal regulations,” McConnell said Thursday morning, describing the move as “yet another example of the lengths they’ll go to defend Obama administration’s regulatory agenda … even when supposedly pro-energy Senate Democrats try to make us think otherwise.”

Democrats have a 16-14 advantage on the Appropriations Committee, but three members of the panel face tough reelection battles in red states this November: Louisiana Sen. Mary Landrieu, Arkansas Sen. Mark Pryor and Alaska Sen. Mark Begich. The new EPA rules, unveiled this month, poll well nationally but the politics are trickier in those states.

Landrieu has spoken out against the EPA regulations, and one of her aides told TPM she was ready to vote for McConnell’s amendment. Aides to Pryor and Begich didn’t immediately return messages seeking comment.

Numerous senior House and Senate Republicans are enthusiastic about using government funding legislation to block the EPA rules on coal. The White House has warned them not to go down that road. A White House official told TPM, “If Republicans want to repeat their government shutdown play to protect the profits of big polluters, they’re placing a pretty risky bet.” The battle becomes tougher for Democrats if they fail to unite against the GOP’s push.

The next steps are unclear. House Republicans have signaled they may target the EPA regulations in their appropriations legislation. The Senate proceeded Thursday on other appropriations measures. Senate Republicans may feel emboldened to withhold support for funding the government if they don’t get to offer their preferred amendments — they’ve blocked several bills over, even the ones they support, over procedural disputes.

Government funding expires on Sept. 30 at midnight. Ultimately it’ll be up to House and Senate leaders whether to rely on the appropriations process or otherwise to strike a deal on a stopgap funding bill to avert a shutdown just one month before the November congressional elections.