Iraq's US-appointed Governing Council has signed an interim constitution at a landmark ceremony in Baghdad.
The ceremony went ahead at the second attempt
The document will take effect when Iraqi sovereignty is restored at the end of June, and is designed to steer Iraq towards free elections.
Shia Muslim spiritual Ayatollah Ali al-Sistani - a leading critic - says it will hamper plans for a permanent constitution in the future.
But US President George W Bush called the adoption an "historic milestone".
The signing of the constitution was meant to have taken place last week but was delayed twice, by objections from Shia members and a series of bloody attacks.
As delegates gathered for the ceremony, explosions were reported in Baghdad.
A BBC correspondent said that smoke was seen rising from near the al-Mansour Hotel, about a kilometre (half a mile) from the Convention Centre where the ceremony took place.
Dozens of guests and delegates, including the US chief administrator in Iraq, Paul Bremer, assembled at the Baghdad complex for a second time after the ceremony was postponed in disarray on Friday.
In a speech before the signing, Council President Mohammed Bahr al-Uloum called the event an "historic moment, decisive in the history of our glorious Iraqi people".
The document signed by all 25 members of the Council, sets out the framework for how Iraq will be governed after the US-led coalition ends the occupation on 30 June and before a new government is chosen by national elections, supposedly by early 2005.
Iraqi Kurds celebrated the event - and Iran and Saudi Arabia welcomed the signing.
President Bush said the signing "marks a historic milestone in the Iraqi people's long journey from tyranny and violence to liberty and peace".
"While difficult work remains to establish democracy in Iraq, today's signing is a critical step in that direction," he said.
But in his first comments, Ayatollah Sistani insisted that only an elected body should sign off further legislation in Iraq.
"Any law prepared for the transitional period will not have legitimacy until it is approved by the elected national assembly," the ayatollah said in a statement.
The ayatollah wields enormous influence over Iraq's Shias, who make up 60% of the country's population.
The BBC's Middle East analyst, Roger Hardy, says the interim constitution is remarkably progressive by the standards of the Middle East, seeking to strike a balance between respect for Islam and regard for liberal democratic rights.
But, he says, wrangling over the document has left a bad aftertaste, exposing a lack of trust between the majority Shia and the minority Kurds and Sunni Arabs - fearful that the new power of the Iraqi Shia will be exercised at their expense.
Five Shia members refused to sign the document last week because of concerns about the power of minorities to veto a future permanent constitution and the composition of the rotating presidency.
A representative of the Shia Supreme Council for the Islamic Revolution in Iraq (Sciri), Abdel Adel Mahdi, told the BBC World Service the Shias still had reservations and that the interim constitution could be amended "later on".