Iraq's president put its prime minister under new pressure to quit on Saturday, saying his resignation would help persuade other parties to form a national unity government that could halt a slide towards civil war.
As at least 12 people were killed in new sectarian violence, the top US military commander in the Middle East called for a broad coalition of the kind Washington hopes can foster stability and allow it to start withdrawing its 133,000 troops.
Convening a first sitting of the new parliament elected in December, Iraq's Kurdish President Jalal Talabani added his public voice to pressure from Sunni, Kurdish and other leaders for Shi'ite Prime Minister Ibrahim al-Jaafari to step aside.
"Opposing Jaafari's nomination is not a personal issue," he said. "It is in the interest of forming a government of national unity."
The Shi'ite United Alliance, by far the biggest bloc in the new parliament, nominated Mr Jaafari to keep his job despite security and economic difficulties and criticism of his handling of violence that has killed more than 500 people since the destruction of a major Shi'ite shrine in Samarra on February 22.
Smaller factions are refusing to join a coalition he leads, however, and rival Shi'ite leaders are considering putting up a new nominee, political sources say.
Parliament is likely to sit around next Sunday, government sources say, but forming a government may take much longer.
"The United Alliance has the right to nominate the prime minister but parliament has to approve it," said Mr Talabani.
The premier must be confirmed by a two-thirds majority.