Some House Democrats are raising the specter of withholding support for must-pass spending legislation later this year in response to President Trump’s hard-line immigration proposals – meaning the fate of roughly 690,000 younger undocumented immigrants could become a major factor in negotiations to keep the government open after December.

Democrats on Monday dismissed Trump’s calls to construct a wall along the entire length of the U.S.-Mexico border, crack down on “sanctuary cities” and seek ways to curb Central American migrants from illegally crossing into the country.

But conservative Republicans insisted that such issues must be addressed before Congress considers offering legal status to immigrants brought to the country illegally as children.

The prospective standoff is the latest hurdle in the years-long struggle on Capitol Hill to reach an accord on reforming the nation’s immigration policy. The administration’s lengthy list of demands dampened growing optimism among lawmakers from both parties that they could strike a deal to protect recipients of Deferred Action for Childhood Arrivals, the Obama-era work program for younger undocumented immigrants that Trump announced last month he would terminate.

“What the White House put forward is a complete non-starter,” House Minority Leader Nancy Pelosi, D-Calif., said in an interview, blaming Trump’s senior policy aides for advancing “un-American” ideas on how to deal with immigration.

“There’s nothing in it to negotiate because it does not have shared values of who we are as Americans,” she said.

Facing a tight deadline – work permits for DACA recipients will begin expiring in March – Pelosi said her conference remains unified in opposition to Trump’s ideas. But comments from Democrats on Monday showed they do not have consensus on how to respond.

Some members of the Congressional Hispanic Caucus signaled they would consider withholding support for must-pass spending bills in December unless the DACA recipients are granted legal status with a path to citizenship. In recent years, near-unanimous support from Democrats has been needed to pass government spending bills and legislation to raise the government’s borrowing limit amid opposition from dozens of fiscal conservatives opposed to increased spending without subsequent budget cuts.

Rep. Luis Gutierrez, D-Ill., called the spending bill debate a defining moment for Democrats.

“I’m not saying we should shut down the government, but if you want a budget with Democratic votes, then it’s got to have some Democratic priorities,” he said.

Rep. Michelle Lujan Grisham, D-N.M., who chairs the Hispanic Caucus, said withholding votes for spending legislation “is definitely on the table,” but she added that Democrats will try to build consensus with moderate Republicans on an immigration plan. Immediately threatening to vote against spending legislation “doesn’t open the door for moderate Republicans,” she said.