The United States again pressed Iraqi leaders Tuesday to form a new government as soon as possible, warning as the new parliament broke up in chaos that "time is not on Iraq's side."

"It was important that Iraq's new parliament convened today, as they pledged to do," State Department deputy spokeswoman Marie Harf said.

"That was a good thing. But we do hope that Iraq's leaders will move forward with the extreme urgency that the current situation deserves."

The new parliament met Tuesday for the first time since April elections. But despite calls for unity, tempers flared and so many Sunni and Kurdish deputies stayed away that the quorum was lost.

US Secretary of State John Kerry visited Iraq last week to try to push the fractious Sunni, Shiite and Kurdish sides to accelerate steps to filling the three key government posts -- speaker, president and prime minister.

The aim is to unify the government and help it confront the threat of Islamic militants who have captured a swathe of northern territory, and declared Iraq and Syria a new Islamic state.

"The fate of Iraq is very much hanging in the balance right now," Harf told reporters.

"Iraq's leaders have a fundamental choice about the future of their country. Do they come together? Do they form a government? Do they say we are going to fight this threat together?"

The new legislature is now due to meet again in Baghdad on July 8.

"It would have been better if they chose a speaker today," Harf told reporters.

"It would be better if they did it before the 8th. But we also understand this is a difficult process. It has a lot of moving parts."

And she disputed the notion that Kerry's message to Iraqi leaders in Baghdad and the semi-autonomous region of Kurdistan in talks last week had gone unheeded.

"Democracy is messy at times," Harf said, adding the leaders of all three communities had vowed in their talks with Kerry that they were committed to the democratic process.

"We now need to see actions back up those words," she added.