President Obama says he's authorised "targeted" airstrikes against Islamist militants in northern Iraq.
He says he's approved the measure to protect US personnel in Irbil if the militants advance towards the city.
The UN Security Council has strongly condemned attacks on Iraqi civilians by Islamic militants.
Tens of thousands of people - mostly Christians - have been forced into the mountains in Northern Iraq where there's no food or water.
Mr Obama also says the US would act to help thousands of Iraqis - mostly Christians - who've fled to the mountains in the north of the country.
