The United Nations has said the humanitarian crisis in Iraq has reached its highest level.
UN special representative Nickolay Mladenov said declaring Iraq a "level three emergency" will help trigger additional goods, funds and assets to respond to the needs of tens of thousands of people displaced by the Islamic State extremist group's offensive.
He said Iraq has been raised to the most serious level "given the scale and complexity of the current humanitarian catastrophe".
Mr Mladenov said tens of thousands of people are reportedly still trapped on Sinjar Mountain "with health conditions quickly deteriorating".
He said the situation in Dahuk, where more than 200,000 displaced Iraqis have fled, is also of "grave concern".
Iraq is the UN's fourth level three humanitarian emergency, joining Syria, South Sudan and the Central African Republic.
Earlier, Iraq's prime minister Nouri Maliki said he would not relinquish power until a federal court rules on what he called a "constitutional violation" by the president to replace him with a member of his own party.
The embattled premier has grown increasingly isolated, with Iraqi politicians and much of the international community lining up behind Haider Ibadi, a fellow member of his Shiite Dawa party tasked by the president with forming a new government that can unite the country in the face of the militant onslaught.
"Holding on (to the premiership) is an ethical and patriotic duty to defend the rights of voters," Mr Maliki said in his weekly televised address to the nation. "The insistence on this until the end is to protect the state."
Mr Maliki vowed legal action against President Fouad Massoum for carrying out "a coup" against the constitution.
"Why do we insist that this government continue and stay as is until a decision by the federal court is issued?" he asked, answering: "It is a constitutional violation - a conspiracy planned from the inside or from out."
Iraqi troops imposed heightened security in Baghdad as international support mounted for a political transition.
Tanks and Humvees were positioned on Baghdad bridges and at major intersections, with security personnel more visible than usual. About 100 pro-Maliki demonstrators took to Firdous Square in the capital, pledging their allegiance to him.
In northern Iraq, thousands of members of the Yazidi religious minority remain stranded in the mountains outside the town of Sinjar, which the Islamic State group captured earlier this month. The Islamic extremists view the Yazidis as apostates and have vowed to kill all those who do not convert.
The Yazidis' plight has prompted a multinational relief effort, with Iraqi and US planes dropping dozens of crates of food and water. An Iraqi helicopter providing aid crashed near the mountain yesterday, killing the pilot, army spokesman Qassim al-Moussawi said. A New York Times reporter and a freelance photographer survived the crash.
The US military has meanwhile targeted the Islamic State group with a series of airstrikes aimed at protecting the Yazidis and slowing the advance of the militants toward Irbil, the capital of the largely autonomous Kurdish region. Yesterday, a US drone destroyed a militant mortar position threatening Kurdish forces defending refugees near the Syrian border.
Another 130 US troops arrived in Irbil yesterday on what the Pentagon described as a temporary mission to assess the scope of the humanitarian crisis on Sinjar Mountain.