US President Barack Obama on Thursday authorised ''targeted'' airstrikes on invading Islamic militants in northern Iraq to protect Americans and help Iraqi security forces to protect civilians under siege, threatening to revive US military involvement in the country's long sectarian war.
He emphasised that he would not commit ground forces and had no intention of letting the United States get dragged back into another war in Iraq.
Obama said he has given nod for "targeted" use of air power to protect US personnel if the Islamic militants advance further toward the Kurdish capital Arbil or threaten Americans anywhere in the country.
"We can act carefully and responsibly to prevent a potential act of genocide,'' Obama told reporters at the White House meeting.
The airstrikes, the first to be carried out by the US military in Iraq since the withdrawal of its forces at the end of 2011, after rampaging militants of Islamic State, an al Qaeda splinter group, drove out tens of thousands of members of Iraq's minority Yazidi sect and left them stranded on the Sinjar mountain.
Many Iraqi Christians have also fled for their lives.
With the refugees on the mountaintop desperately short of food, water and medicine, Obama said, the US has already started military airdrops of humanitarian supplies to besieged religious minorities to prevent a "potential act of genocide''.
Washington has been forced to act after the Islamic State militants, who routed the Iraqi military in the north and seized large swaths of territory in recent months, made recent gains against Kurdish forces and moved toward Arbil, capital of the Kurdish semi-autonomous region.
News photographs, meanwhile, showed Islamic State fighters at a checkpoint at a border town in Iraq's semi-autonomous Kurdish region, a little over 30-minute drive from Arbil, headquarters of the Kurdish regional government and a business centre.
"We intend to stay vigilant and take action if these terrorist forces threaten our personnel or facilities anywhere in Iraq, including our consulate in Arbil and our embassy in Baghdad.'' he said.
With targeted air strikes, Obama hopes to halt the militant advance and shift the balance on the battlefield in favour of embattled Iraqi and Kurdish forces.
A small number of US military advisers are already in Iraqi to help Bhagdad fend off the Islamic militant offensive, but was yet reluctant to take direct military action.
The Islamic State's Sunni militants view Iraq's majority Shi'ites and minorities such as Christians and Yazidis - a Kurdish ethno-religious community - as infidels. Obama, however, blames Iraq's Shi'ite Prime Minister Nuri al-Maliki for the Iraqi government's failure to defuse the crisis.