The legal and political standoff has become a major test of Congress’ authority over war powers more than 50 years after the law was passed in the aftermath of the Vietnam War.
While most Republicans have continued to back Trump, the expiration of the 60-day window had been viewed by some lawmakers as a potential turning point in support for the conflict, which has entered its 75th day amid rising costs and growing concern over US military readiness.
Merkley acknowledged before the vote that the administration had “complicated” the issue by declaring the clock paused.
Despite the defeat, Democrats have been cheered by a slowly growing number of Republican defections.
Three of Trump’s senators crossed the aisle to support the resolution - one more than in the previous vote in April – giving the President the narrowest of winning margins, at 50 votes to 49.
The War Powers Act has historically proven difficult to enforce, with courts generally reluctant to intervene in disputes between Congress and the White House over military action.
Even if a resolution were eventually to pass the Senate, it would still face steep hurdles in the Republican-controlled House and would likely be vetoed by Trump.
- AFP