The threat, voiced by multiple sources, marks the clearest indication yet that President Donald Trump might not get Congress to foot the bill for the wall, imperiling his central goal that he made a centerpiece for his campaign.
Trump and GOP leaders have discussed advancing a new funding package that could cost upwards of $15 billion to pay for the wall -- as the new president has promised that Mexico will ultimately reimburse the United States for the project.
But many in both parties are skeptical that Mexico will pay for the wall as the country has insisted that it would not foot the bill. And it's unclear how Trump's funding package will be paid for or if it would be offset by new spending cuts.
With 52 Republicans, the party would need eight Democratic senators to break a likely filibuster. Democratic sources are already confident that most, if not, all of their members will join forces to try to block the plan. Even some fiscal conservative Republicans may balk at the price tag.
White House press secretary Sean Spicer said Thursday that the administration was considering a 20 percent tax on Mexican imports, but later said it was just one option under consideration.
Democrats are pushing back.
"Instead of having Mexico pay for the Wall, President Trump, Speaker Ryan and Washington Republicans would have the American middle-class pay for the wall," Senate Minority Leader Chuck Schumer, D-New York, said in a Friday statement. "The costs for everything from groceries, to cars, to office supplies would go up by 20%, making it harder for middle-class families to pay for things they need every day."
The full Democratic caucus has yet to fully discuss its strategy because the bill has not yet been drafted, sources say. But Democrats believe that they will have the votes to block the bill in the Senate, especially if the money is not offset with spending cuts since even the conservative Democrats are likely to revolt, sources say.
On Thursday, Ryan and Senate Majority Leader Mitch McConnell wouldn't say how the plan would be paid for, saying they would wait for the administration to submit its plan to Congress.
"We are moving ahead, as the speaker pointed out yesterday, roughly $12 to $15 billion," McConnell said. "We intend to address the wall issue ourselves."
Ron Wyden, the top Democrat on the Senate Finance Committee, said there are many unanswered questions about border adjustment and that he's unsure it has much of a clear path on Capitol Hill.
"People are going to be worried they're going to go into a grocery store and stuff costs a lot more," Wyden, whose committee position makes him the point person on tax reform for Democrats in the Senate, told CNN in an interview. Pointing to Texas GOP Sen. John Cornyn's skepticism over the plan White House Chief of Staff Reince Priebus called one of a "buffet" of options being considered finance the border wall with Mexico, Wyden said critical Senate Democrats may not have to stand up to the idea alone.
"Based on the last 24 hours, I think Republicans are going to tank that one on their own," he said.