It was also mulling air strikes against the militants, who are led by the jihadist Islamic State of Iraq and the Levant but include loyalists of now-executed Sunni Arab dictator Saddam Hussein. Meanwhile, the United Nations warned Iraq is in danger of disintegrating.
A relative calm in Baghdad - ostensibly as militants have focused on their northern assault - was shattered by a string of bombings that left 17 people dead, while the bodies of 18 soldiers and police were found near the city of Samarra, all shot in the head and chest.
Since the insurgents launched their lightning assault on June 9, they have captured Mosul, a city of two million people, and a big chunk of mainly Sunni Arab territory stretching towards the capital.
The offensive has displaced hundreds of thousands of people and sent jitters through world oil markets as the militants have advanced ever nearer Baghdad leaving the Shiite-led government in disarray.
Officials said on Tuesday that militants briefly held parts of the city of Baquba, just 40 miles from the capital.
They also took control of most of Tal Afar, a strategic Shiite-majority town between Mosul and the border with Syria, where ISIL also has fighters engaged in that country's three-year-old civil war.