Washington vowed Wednesday to boost aid to Iraq and is mulling drone strikes amid fears Iraqi forces are crumbling in face of militants increasingly emboldened since the U.S. withdrawal.
Iraqi officials have already privately asked the U.S. to consider sending in drones to root out militants from the Islamic State of Iraq and the Levant (ISIL), who in a lightning offensive have seized a swathe of the north.
The request has been turned down in the past, but Washington is now weighing possibilities for more military assistance to Baghdad, including drone strikes, a US official told AFP on condition of anonymity.
Resorting to such aircraft — which remain highly controversial in Afghanistan and Pakistan — would mark a dramatic shift in the U.S. engagement in Iraq, after the last American troops pulled out in late 2011.
"The United States has been fast to provide necessary support for the people and government of Iraq," National Security Adviser Susan Rice told a Washington think-tank.
"We are working together to roll back aggression and counter the threat" posed by ISIL to Iraq and the region, Rice said.
But she insisted the US "must do more to strengthen our partners' capacity to defeat the terrorist threat on their home turf by providing them the necessary training, equipment and support."
State Department spokeswoman Jen Psaki stressed there were no current plans to send U.S. troops back to Iraq, where around 4,500 Americans died in the eight-year conflict.
She also denied the offensive, in which the militants seized northern Mosul and then Tikrit, had caught Washington by surprise or marked a failure of U.S. policy in the country it invaded in 2003.
The United States has repeatedly warned of the dangers of ISIL and has already expedited arms shipments to Iraq this year and ramped up training for Iraqi security forces.
White House spokesman Jay Carney said the U.S. would "stand with Iraqi leaders across the political spectrum as they forge the national unity necessary to succeed in the fight against ISIL."
The U.S. would also provide "and as required increase, assistance to the government of Iraq to help build Iraq's capacity to effectively and sustainably stop ISIL's efforts to wreak havoc in Iraq and the region," he added in a statement.
In January, Washington sold 24 Apache attack helicopters to Baghdad, as well as about 300 anti-tank Hellfire missiles and two of some 36 F-16 fighter aircraft, according to a Pentagon spokesman.
Some of the arms have been delivered and others will soon be on their way.
A request for a further $1 billion in aid, including provisions for around 200 Humvee vehicles and 24 AT-6C Texan II aircraft, is before Congress.
The last U.S. troops left Iraq in December 2011, eight years after ousting Saddam Hussein following the invasion ordered by then president George W. Bush.
Since then, Washington has provided training to Iraq's military for counterterrorism missions, including in Jordan since early 2014.
U.S. Vice President Joe Biden meanwhile called for the "safe and immediate" return of 49 Turkish citizens kidnapped from a consulate in Mosul.
During a call with Turkish Prime Minister Recep Tayyip Erdogan, Biden said "the United States is prepared to support Turkey's efforts to bring about the safe return of its citizens."
U.S. officials also said they would try to help an estimated 500,000 people displaced from Mosul.