The US military said a suicide bomber had driven a truck loaded with explosives into a police station in eastern Baghdad. Most of the victims were thought to be civilians.

The attack came as the president of Iraq, Jalal Talabani, tried to calm anxiety among liberals and secular figures that the constitution, which is being considered by the Shia-dominated legislature, will give undue prominence to Islamic law.

Adding to the alarm of secularists, as well as Iraq's non-Muslim minorities, conservative Shia members on the drafting committee are pressing for the country to be renamed the Islamic Republic of Iraq.

Mr Talabani told the Guardian that Iraq would never become an Islamic state, but would enshrine federalism, democracy and pluralism.

"Human rights and individual liberties, including religious freedom, will be at the heart of the new Iraq," the president said at his residence in Baghdad.

A senior presidential aide said there was "no way" that Mr Talabani would allow the country to be renamed.

The proposal was made by Amar al Hakim, the son of Abdul Aziz al Hakim, leader of the Supreme Council of Islamic Revolution in Iraq, and head of the Shia bloc in parliament.

Secular Kurds have suggested the country be named the Federal Republic of Iraq, while Sunni Arabs have suggested the Arab Republic of Iraq.

The Iraqi president does not have a direct role in drafting the constitution, but as head of the Kurdish bloc in the national assembly, the junior partner in the Shia-led coalition government, he has an effective veto.

A referendum on the new constitution, which is supposed to be ready by August 15, is scheduled for October 15. If the document is approved, there will be a general election on December 15.

But under a clause in Iraq's transitional administrative law (Tal), the referendum on the permanent constitution will fail if two thirds of the population in any three provinces reject it - even if it gains a majority nationwide. The Kurds, who control Iraq's three northern provinces, inserted the clause to guard against encroachment on their self-rule.

Mr Talabani said he believed the role of religion in Iraq should remain as set out in the country's interim constitution.

That document, drawn up in spring 2004, states that "Islam is the official religion of the state and is to be considered a source of legislation".

In the new constitution, Shia hardliners have been pushing for Sharia law to be considered as the "primary" source of legislation, and for inheritance, marriage and divorce to be subject to religious authorities.

Mr Talabani said it took "long hours of discussion and debate to reach the Tal, a document that enshrines many good principles that the Iraqi people have longed for for years". He said: "These controversial issues [the relation between Islam and the state] were settled in the Tal in an acceptable way. If we allow that door to open again, nobody knows how it would get closed."

With three weeks until the deadline, discussions remained in limbo yesterday as committee members waited to see if Sunni Arabs would rejoin the process. They walked out last week after the assassination of Mijbil Issa, a Sunni member of the drafting council, by gunmen in Baghdad.

Sunni Arabs form the backbone of the insurgency and their participation in drafting the constitution is regarded as essential to prevent the further alienation of the once-dominant minority.

Meanwhile, other attacks around the capital left three people dead, including two police officers.

A police lieutenant colonel was killed in northern Iraq.

· One US soldier was killed and two were wounded yesterday during a mortar attack near Balad, north of Baghdad, the US military said.