WASHINGTON — North Carolina’s Thom Tillis on Monday became the second Republican to promise a vote to block President Donald Trump’s declaration of an emergency at the Mexican border.

Tillis said Congress must defend its power of the purse and warned that a future Democratic president might abuse the power to advance “radical policies.”

He revealed his view a day before the Democratic-run House was set to vote to annul Trump’s emergency declaration, which he made Feb. 15. The declaration would give Trump access to billions of dollars beyond the nearly $1.4 billion that Congress approved to build segments of barriers along the boundary with Mexico.

While Republicans control the Senate 53-47, it seems likely there would be enough GOP defectors for the measure to win initial approval there. The bill would need a simple majority to pass, and four Republican defectors joining all Democrats and their two independent allies would suffice. Trump has promised a veto and it seems all but certain that Congress won’t be able to muster the two-thirds majorities required to override a veto.