The Republican-controlled US Senate passed a resolution on Tuesday that seeks to limit President Donald Trump’s power to wage war against Iran.
In a 50 to 48 vote, the Senate voted to direct Mr Trump to remove the US military from hostilities against the Iran, "other than those elements of the Armed Forces that may be necessary to defend the US or an ally or partner of the US from imminent attack”.
The resolution does not require Mr Trump’s signature, so it may not carry the full weight of the law, although Democrats insist it does.
Regardless, critics will cast the resolution as emblematic of his waning influence in his Republican Party.
Four Republican senators joined Democrats to pass the resolution, which is a continuation of a bill that was passed several weeks ago by the Republican-controlled US House of Representatives.
Democratic Senator Adam Schiff said the Trump administration had pursued an "illegal war without making the case to Congress or the American people".
“In the months since, we’ve seen the region in chaos, shifting goalposts and rationales for the war, skyrocketing gas and grocery costs, and tragically, the lives of 13 service members lost with thousands more put in harm’s way," Mr Schiff said in a statement.
“Now, the administration has capitulated with a complete giveaway to Iran that leaves our national security far worse than when the war began."
The timing of the Senate resolution, with the conflict in Iran on hold, is likely to blunt its overall influence.
The war has proved unpopular in the US. Just one in four Americans believes Mr Trump's war was worth its costs and most worry that a truce with Tehran is unlikely to last, a Reuters/Ipsos poll released on Tuesday found.
Mr Trump did not immediately react to the Senate resolution.
Hostilities between the US and Iran have ceased since they signed an interim peace deal last week, but tension remains high and sticking points persist as the two countries try to reach a final agreement.
