The Senate voted 51-47, almost entirely along party lines, on a procedural measure blocking the war powers resolution, with members of Trump's party arguing that the United States was not currently participating in hostilities against Cuba.
Republican Senator Rick Scott of Florida, who initiated the procedure that stopped the resolution, said a vote on war powers was inappropriate because Trump had not deployed troops.
Democratic Senator Tim Kaine of Virginia, one of the main sponsors of the measure, argued that US efforts to stop fuel shipments to the communist-ruled island amounted to military action.
“If someone were to do to the United States what we are doing to Cuba, we would definitely consider it an act of war,” Kaine said in a Senate speech before the vote.
Under Trump, US forces have carried out attacks on ships off the coast of Venezuela and entered Caracas to capture President Nicolas Maduro, and together with Israel have waged war against Iran since February 28 — all without congressional approval.
Trump has declared that "Cuba is next," without specifying what he plans to do, but has often claimed that its government is on the verge of collapse.
Democrats have repeatedly tried unsuccessfully, in both the Senate and the House of Representatives, to force Trump to obtain congressional approval for military operations.
Republicans, who have a narrow majority in both houses, have almost unanimously rejected such resolutions, accusing Democrats of trying to weaken Trump through the war powers act.
Although the US Constitution stipulates that war can be declared by Congress, not the president, that restriction does not apply to short-term operations or responses to an immediate threat.
The White House argues that Trump's decisions are consistent with his rights and obligations as commander in chief to protect the United States.
