The leader of Iraq's biggest Shiite political party on Tuesday described the nation's interim constitution as a "huge achievement" but echoed criticism by an influential Shiite cleric that parts of the document encroached on the powers of a future elected parliament.

In Balad Ruz, north of Baghdad, a U.S. 1st Infantry Division (search) soldier was killed — the first to die in combat since March 2 — and another was wounded after a roadside bomb exploded, Maj. Debra Stewart said.

Stewart said the soldier was also the first member of the 1st Division to be killed in Iraq since it began rotating in last month to replace the 4th Infantry Division.

In Kirkuk (search), celebratory gunfire at a rally marking the signing of the interim constitution left three Kurds dead and 21 others injured, Police Chief Gen. Torhan Youssef said. The deaths Monday were accidental, he said.

The U.S.-picked Iraqi Governing Council signed the temporary constitution on Monday, a key step in U.S. plans to hand power to the Iraqis by July 1.

"Our main problem lies with the imposition of restrictions set by an unelected body on an elected body," said Abdel-Aziz al-Hakim, leader of the Supreme Council for the Islamic Revolution in Iraq (search) and a member of the U.S.-appointed council.

"No one believes that this document reflects perfection or embodies the ambitions of everyone," he told a news conference Tuesday.

Al-Hakim's criticism reiterated that of the Shiites' most influential cleric, Grand Ayatollah Ali al-Husseini al-Sistani (search), who issued a religious edict on Monday saying the document will gain legitimacy only when adopted by an elected assembly.

Al-Sistani's supporters on the Governing Council pledged to try and amend parts of the charter. Al-Hakim, who maintains close ties to al-Sistani, said they would seek the consensus of council members on any amendments.

On Tuesday, a senior Shiite cleric from the holy city of Karbala also criticized clauses pertaining to federalism in the document, warning that they could lead to the dismemberment of Iraq or plunge the nation into civil war.

Grand Ayatollah Mohammed Taqi al-Modaresi (search), whose views are respected but who commands a much smaller following than al-Sistani, said in a statement that the interim charter's adoption of a federalist system would be "a time bomb that will spark a civil war in Iraq if it goes off."

In contrast, President Bush praised the 22-page charter, saying its adoption was a "historic milestone in the Iraqi people's long journey from tyranny and violence to liberty and peace."

Bahr al-Ulloum, an elderly Shiite cleric who heads the council, described the signing of the new charter as a "historic moment, decisive in the history of Iraq."

Most of the council's 13 Shiite members, including Bahr al-Ulloum, refused at the last minute to sign the document Friday, citing al-Sistani's opposition. During talks over the weekend, al-Sistani signaled to the Shiites that they could sign despite his reservations.

Bahr al-Ulloum's fellow Shiites on the U.S.-appointed council said they would sign for the sake of national unity and to keep the political process moving forward.

"We say here our decision to sign the document is pegged to reservations," Ibrahim al-Jaafari, a senior Shiite council member, told reporters after the ceremony. "In reality, we had a choice between delaying the constitution or dealing with our reservations, particularly on two clauses, in an annex."

The annex will decide the shape of the Iraqi government that will take over from the U.S.-led occupation authorities June 30.

The more important of the two clauses in dispute, according to al-Jaafari, would give Kurds and Sunni Arabs a de facto veto over a permanent constitution.

It stipulates that if two-thirds of voters in any three of Iraq's 18 provinces reject it, then the document cannot be adopted, parliament is dissolved and a general election is held. Kurds make up the overwhelming majority of three northern provinces where they've enjoyed self-rule since 1991.

Kurds and Sunnis, who combine for 30-40 percent of Iraq's 25 million people compared to the Shiites' 60 percent, see the clause as a safeguard against the domination of the Shiite majority. Shiite politicians countered that leaving the clause unchanged gives a minority of as little as 10 percent of the population the power to block the will of the remaining 90 percent.

Iraq's permanent constitution will be drafted by a legislature elected by Jan. 31, 2005 and the Shiites politicians said the clause in question, if left unchanged, will encroach on the powers of the elected body.