The US Senate has failed to advance the $1.15 trillion annual National Defence Authorisation Act (NDAA), after a vote fell short of the threshold needed to move the legislation forward.
The measure failed 50-46, falling short of the 60 votes required to proceed.
The vote largely split along party lines, with Senate Majority Leader John Thune switching his vote from "yes" to "no" to preserve the option of bringing the motion back for reconsideration at a later date.
Four senators were absent from the vote: John Fetterman, Jim Justice, Mitch McConnell and Alex Padilla.
Funding disputes
The NDAA was approved by the Senate Armed Services Committee last month in an 18-9 bipartisan vote, but divisions between Republicans and Democrats have intensified in recent weeks.
Lawmakers have been unable to resolve disagreements over overall defence and non-defence spending caps, preventing the legislation from advancing on the Senate floor.
Democrats have also cited the renewed US military conflict with Iran as a key reason for opposing the procedural motion.
They criticised President Donald Trump's decision not to seek congressional authorisation for the military operation, which began on February 28, arguing that the administration bypassed Congress in launching the campaign.
The failed vote leaves the annual defence authorisation bill stalled in the Senate, with Republican leaders expected to revisit the measure at a later stage.
