US Pentagon chief Pete Hegseth faced tough questioning from lawmakers on Tuesday as he defended the growing cost of the US military campaign against Iran.

Speaking before the Senate Appropriations Committee, Hegseth said the conflict has so far cost $37.5 billion (€32.89 billion), a figure significantly higher than earlier estimates.

He argued that additional funding is urgently needed, warning that the military faces critical shortfalls without it.

The hearing was repeatedly interrupted by protesters and came days after the Pentagon confirmed that three more US service members had died in the conflict, bringing the American death toll to 17.

Democratic senators challenged both the cost and direction of the war.

Senator Patty Murray warned of "another forever war," while other lawmakers questioned why the Pentagon was seeking more funding when some previously approved military spending has yet to be used.

The debate comes as Republicans push a $95 billion budget package that includes tens of billions for the military and national security, as well as funding for agriculture and election-related measures.

Meanwhile, opinion polls suggest many Americans remain critical of US President Donald Trump's handling of the conflict as fighting with Iran continues.