The crisis in Iraq has raised alarm in the United States and Iran, both of whom support the al-Maliki government.
The two long-time foes even discussed ways to stop the violence Monday on the sidelines of separate nuclear negotiations in Vienna, Austria.
Although the United States dismissed speculation of US-Iranian military cooperation, Secretary of State John Kerry said the US was "open to any constructive process."
State Department spokeswoman Jen Psaki said any discussion with Iran would concern ways Iran could help press al-Maliki's government to be more inclusive and treat all of Iraq's religious and ethnic groups equally.
Any talks with Iran "would be to discuss the political component here and our interest in encouraging Iraqi leaders to act in a responsible, nonsectarian way," she told reporters. "Certainly a discussion of that is something that we would be open to."
Meanwhile, the White House on Sunday began its deployment of up to 275 US soldiers in Baghdad "to provide support and security for US personnel and the US Embassy in Baghdad," according to US President Barack Obama.
While the force was being deployed for the purpose of protecting US citizens and property, the personnel were still equipped for combat, Obama said in a report to Congress.
"This force will remain in Iraq until the security situation becomes such that it is no longer needed," he said
The Obama administration said it was mulling a range of options in support of Baghdad, including air strikes as requested by the Iraqi government, but would not send in US ground troops.
While the White House continues to review its options, Iran's military leaders are already taking action.
The commander of Iran's elite Quds Force, Gen. Ghasem Soleimani, consulted with the Iraqi government Monday on how to halt the insurgents' advance.
According to media reports, Soleimani has been inspecting Iraqi defenses and reviewing plans with top commanders and Iranian-backed Iraqi Shiite militia.
UN Secretary-General Ban Ki-moon has condemned the recent upsurge of violence in Iraq.
A statement issued by Ban's spokesperson Sunday night said reports of mass summary executions by ISIL were deeply disturbing and underscored the urgency of bringing the perpetrators of such crimes to justice.
Saudi Arabia said Monday it rejected any foreign intervention in Iraq's domestic affairs as the country was trying to turn around a worsening security situation.
The Sunni-dominated country blamed Baghdad's "sectarian and exclusionary policies" for fuelling the insurgency.
Neighboring Turkey is sending humanitarian aid to the violence-hit cities of Iraq, particularly to the Turkmen-populated areas, while Jordan is closely following the situation and its army is on alert to protect the country from any spillover effects.