Iraq's Governing Council said today the signing an interim constitution would take place on Friday.
The council this morning delayed the signing because of the attacks which killed at least 170 people yesterday.
A wave of suicide bombings and mortar attacks on crowds of Shia Muslim worshippers killed at least 170 people in Baghdad and Kerbala yesterday.
More than 435 others were wounded in the attacks that officials said were aimed at igniting sectarian war.
It was Iraq's bloodiest day since Saddam Hussein was toppled. The coordinated blasts targeted Shia marking the holy period of Ashura with mass gatherings in Iraqi cities.
The Governing Council declared a three-day mourning period starting today when Council members were scheduled to sign an interim constitution seen as a key stage in US plans to return sovereignty to Iraqis on June 30th.
Leaders of the country's 60 per cent Shia majority called for calm while the Governing Council blamed the attacks on a Jordanian, Abu Musab Zarqawi, who Washington says is working for al Qaeda and trying to fuel chaos in Iraq.
US forces have placed a $10 million bounty on his head. They said last month they had intercepted a computer disk with a letter from Zarqawi urging suicide bomb attacks on Shias to inflame sectarian tension in Iraq.