US President Barack Obama has welcomed moves by Iraq's president to appoint a new prime minister, Haider al-Abadi, calling it a promising step forward.
Mr Obama acknowledged that Iraq had been through "difficult days". He said he has spoken to Mr Abadi and urged him to quickly form a government that will unite all of Iraq's different communities.
Earlier on Monday, Iraq's president asked Mr Abadi to form a new government, snubbing the incumbent Prime Minister Nouri Maliki.
Mr Maliki said Mr Abadi's nomination was a "violation of the constitution", the BBC reports.
Mr Obama said US forces had successfully carried out air strikes to prevent the advance of Islamist militants in northern Iraq. However, he said there was no American military solution to the crisis - and that only an inclusive Iraqi government could unify the fight against the Islamists.
Militants from the Islamic State (IS) group have made substantial gains in northern Iraq in recent months, forcing tens of thousands of people from religious minorities to flee their homes.
Iraq minority begins leaving mountain
Thousands of people from an Iraqi religious minority trapped on a mountain by Islamic State militants have been able to escape with help from Kurdish security forces and others, the UN says.
Many more are still trapped on Mount Sinjar in northern Iraq, where harsh summer conditions have taken scores of lives.
The US and Britain have air-dropped humanitarian aid in recent days to Yazidis trapped in searing heat, and Washington has bombed the Islamic State Sunni insurgents in its first military action in Iraq since withdrawing troops in 2011.
The US says it has begun supplying weapons to the Iraqi Kurdish forces fighting the jihadists.
It was taking limited action to protect a Kurdish autonomous region and prevent what US President Barack Obama called a potential "genocide" of religious minorities targeted by the militants, Washington says.
The Yazidis fled to Mount Sinjar last week to escape the Islamist militants who deem Yazidis "devil worshippers", Reuters reports. The Yazidis follow an ancient faith derived from Zoroastrianism.
An official in the UN Office for the Coordination of Humanitarian Affairs said thousands had been able to escape in the past three days. Air drops of aid were critical to keeping those still on the mountain alive until an escape route could be secured, spokesman Kieran Dwyer said.
The UN mission in Iraq has said it is preparing a humanitarian corridor to allow Yazidis to flee.