Senate Minority Leader Chuck Schumer said Democrats will not vote for a must-pass government funding bill next month if it includes money for construction of a wall along the U.S.-Mexico border.

"That will not stand," Schumer, D-N.Y., warned Monday in a Senate floor speech. "It would be inappropriate in our judgement to insist on the inclusions of such funding in a must-pass appropriations bill that is needed by the Republican majority to avoid a government shutdown."

A short-term funding measure expires in April.

Republicans, who control majorities in both chambers, have not indicated what they plan to include in a bill that would fund the government for the remainder of the fiscal year. Some options include supplemental funding for the military or additional money for building the border wall that President Trump promised during his campaign.

Schumer said if border wall funding is included, it would constitute a "poison pill" that Democrats would vote against.

"The president wants a wall, but he hasn't answered so many questions about it," Schumer said. "What about eminent domain? What's the design of the wall? Where is it going to be located? How is it going to be paid for and how much is it going to cost?"

Schumer, quoting a Trump campaign promise, added, "Don't you think we should give time for Mexico to pay for the wall?"

Federal funding runs out on April 28. Republicans will need eight Democrats to support a new spending bill in order to avoid a filibuster.

Democrats sent a letter earlier Monday to Majority Leader Mitch McConnell, R-Ky., expressing "interest" in working with the GOP on a spending deal and warning against including border wall funding.