GOP leaders had delivered the sweeping spending proposal to the Democrats on Tuesday evening as Congress scrambles to fund the government and prevent a shutdown ahead of a looming Dec. 11 deadline.

But Democratic leaders said "more than 30" Republican policy amendments, known as riders, made the package unacceptable, according to a senior Democratic aide familiar with the budget talks.

Those appropriators are now working on a counter-offer to the GOP bill, the aide said.

"We haven’t been talking to the press, we’ve been respectful, we’ve been open, understanding that we have to compromise and the rest — and then all of a sudden, they announce, ‘We’re telling the Democrats time is running out,’" House Minority Leader Nancy Pelosi (D-Calif.) told fellow Democrats Wednesday morning, according to the senior aide. "Well, we told them to have this done by Nov. 20 — before we left so the staff could work on it the next week into Thanksgiving."

The GOP offer followed a roughly 30-minute phone call between Ryan and Pelosi on Tuesday, another source familiar with the negotiations said. During the call, the Speaker urged Pelosi to allow the Appropriations Committee to do its work given that time is running short.

And Ryan urged Pelosi to consider the offer put forth by GOP Appropriations Committee negotiators, the source said.

"The proposal was an Appropriations Committee offer, constructed by the Appropriations Committee. The speaker supported it, but he's deferring to Chairman Rogers," Ryan spokeswoman AshLee Strong said.

Among the riders rejected by the Democrats are provisions scaling back environmental regulations and undoing parts of the Dodd-Frank Wall Street reform law of 2010, the aide said.

The Democrats also rejected a Republican amendment to toughen the screening process for refugees fleeing violence in Syria and Iraq. GOP leaders had pushed that bill, sponsored by Homeland Security Chairman Mike McCaul (R-Texas), through the lower chamber last month as an emergency response to the deadly terrorist attacks in Paris.

The bill won the support of 47 House Democrats, but party leaders rejected it as an attempt to end the refugee program altogether, and President Obama has vowed to veto the language if it hits his desk.

Trying to avoid a shutdown, which damaged the Republicans in 2013, GOP leaders are eying another anti-terror amendment that could serve as a substitute to the McCaul provision. The alternative proposal is designed to strengthen the current visa-waiver program, making it tougher for some foreigners to visit the United States in the name of national security.

This story was updated at 12:15 p.m.

Citing dozens of "poison-pill" riders, House Democrats have rejected the Republicans' initial year-end government funding bill and plan to respond with their own alternative package.