WASHINGTON — The Senate will vote Wednesday on whether to cut off American military assistance for Saudi Arabia’s war in Yemen, preparing again to rebuke President Trump for his continued defense of the kingdom after the killing of the dissident journalist Jamal Khashoggi.

The Yemen vote sets up something of a one-two punch for senators hoping to defy the president. The second punch may land Thursday, when the Senate has the chance to give final passage to a resolution overturning the president’s declaration of a national emergency to secure funding for his border wall.

Passage of the measures would prompt the first vetoes of Mr. Trump’s presidency.

“The resolution we will vote on in the Senate tomorrow to end U.S. support for the Saudi-led war in Yemen is enormously important and historic,” Senator Bernie Sanders, independent of Vermont, said Tuesday in a statement. “This war is both a humanitarian and a strategic disaster, and Congress has the opportunity to end it.”

Supporters of the Yemen resolution have faced a long and grueling road to get the legislation onto the president’s desk. The Senate — led by the resolution’s authors, Mr. Sanders, Mike Lee, Republican of Utah, and Christopher S. Murphy, Democrat of Connecticut — first passed the measure 56 to 41 in December, but Paul D. Ryan, the speaker at the time, refused to take up the resolution.