US President Barack Obama has formally notified Congress that he had authorised "limited" air strikes in Iraq to help security forces, which retook the country's largest dam earlier from militants.
National Security Council spokeswoman Caitlin Hayden said on Sunday the air strikes were consistent with the War Powers Resolution, which requires congressional approval before the president can launch the country into war.
The strikes have been conducted since Friday at the request of the Iraqi government, according to Hayden.
Backed by the US war planes, Iraqi Kurdish fighters retook Mosul dam on the weekend.
It marked the biggest prize yet clawed back from Islamic State militants since they launched a major offensive in northern Iraq in early June.
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"On the evening of August 15, 2014, US military forces commenced targeted air strike operations in Iraq," Obama said in his letter to the speaker of the House and president pro tempore of the Senate.
"These military operations will be limited in their scope and duration as necessary to support the Iraqi forces in their efforts to retake and establish control of this critical infrastructure site."
Highlighting the stakes at hand, Obama noted that "the failure of the Mosul dam could threaten the lives of large numbers of civilians, endanger US personnel and facilities, including the US Embassy in Baghdad, and prevent the Iraqi government from providing critical services to the Iraqi populace".
Earlier, US Central Command said its forces conducted 14 air strikes, damaging or destroying 10 armed vehicles, seven Humvees, two armoured personnel carriers and one checkpoint operated by the militants.
Another nine US air strikes were conducted on Saturday.
Since the War Powers Resolution was enacted in 1973, a succession of American presidents have unilaterally initiated military strikes or land invasions on numerous occasions without Congressional approval, invoking their constitutional authority as commander in chief.
