WASHINGTON — House Democrats will file a resolution Friday aimed at blocking the national emergency declaration that President Donald Trump has issued to help finance his wall along the Southwest border, teeing up a clash over billions of dollars, immigration policy and the Constitution’s separation of powers.

Though the effort seems almost certain to ultimately fall short — perhaps to a Trump veto — the votes will let Democrats take a defiant stance against Trump that is sure to please liberal voters. They will also put some Republicans from swing districts and states in a difficult spot.

Formally introducing the measure sets up a vote by the full House likely by mid-March, perhaps as soon as next week, because of a timeline spelled out by law. Initial passage by the Democratic-run House seems assured.

The measure would then move to the Republican-controlled Senate, where there may be enough GOP defections for approval. The law that spells out the rules for emergency declarations seems to require the Senate to address the issue too, but there’s never been a congressional effort to block one and some procedural uncertainties remain.

Should the House and Senate initially approve the measure, Congress seems unlikely to muster the two-thirds majorities in each chamber that would be needed later to override a certain Trump veto.

Even so, Republican senators facing tough re-election fights next year in competitive states like Arizona, Colorado and North Carolina would have to take stances that could risk dividing the GOP’s pro-Trump and more moderate voters.

Moderate Sen. Susan Collins R-Maine said Wednesday she would back a resolution blocking the emergency declaration, making her the first Republican to publicly state her support for the effort to thwart the emergency. With Republicans holding a 53-47 majority, three more GOP senators would need to vote with Democrats for the resolution to win initial approval.

The votes could also cause discomfort for other Republicans who’ve opposed the declaration.

Many have expressed concerns that Trump’s declaration sets a precedent for future Democratic presidents to declare emergencies to help their own favored issues, like global warming or gun control.

The battle is over a declaration that Trump, whose wall was the most visible trademark of his presidential campaign, issued last week to access billions of dollars beyond what Congress has authorized to start building border barriers.

Congress approved a vast spending bill last week providing nearly $1.4 billion to build 55 miles of border barriers in Texas’ Rio Grande Valley while preventing a renewed government shutdown. That measure represented a rejection of Trump’s demand for $5.7 billion to construct more than 200 miles.

Besides signing the bill, Trump also declared a national emergency and used other authorities that he says gives him access to an additional $6.6 billion for wall building. That money would be transferred from a federal asset forfeiture fund, Defense Department anti-drug efforts and a military construction fund. Federal officials have yet to identify specifically which projects would be affected.