Iraq's parliament has approved six new ministers to fill key contested cabinet posts, but one nominee immediately refused to join the government.
Violence has surged since the government was formed
Hashim al-Shible, a Sunni Arab, turned down the post of human rights minister.
Prime Minister Ibrahim Jaafari seemed to have agreed all but one of the seven remaining posts, giving four to Sunnis.
The BBC's Jim Muir in Baghdad says Mr Jaafari hoped to cut the ground from insurgents within their community by bringing Sunnis into government.
There has been an upsurge in violence around the country since the formation of the government in late April.
At least 250 people have died.
In the latest incident on Sunday, police said a senior civil servant from the transport ministry, Zobaa Yassin, had been shot dead in his car with his driver.
The new ministers had been expected to take the oath of office later on Sunday.
Defence: Dr Saadoun al-Dulaimi (Sunni)
Oil: Dr Ibrahim Bahr al-Uloum (Shia)
Deputy prime minister: Abid Mutlak al-Jubouri (Sunni)
Electricity: Dr Mohsen Shlash (Shia)
Industry: Usama al-Najafi (Sunni)
Human Rights: Hashim al-Shible (Sunni)
But Mr Shible rejected his post, saying he had not been consulted about the appointment and was selected only because he was a Sunni.
"Concentrating on sectarian identities leads to divisions in the society and state, and for that reason I respectfully decline the post," he said, quoted by AP news agency.
Mr Jaafari had sought a deal with Sunni Arabs over the cabinet, hoping to stem a rise in insurgent violence.
"We will take all necessary steps to fight this monstrous phenomenon," he said later of the insurgency.
He said officials had not been wasting time but that extended discussions had been necessary.
"We were careful to involve all political protagonists and this explains the delay in forming the government," he said.
The most sensitive positions are the defence and oil portfolios.
Saadoun al-Dulaimi, a Sunni Arab with roots in an area which is a hotbed of the insurgency, has been named defence minister.
He is a respected psychologist and statistician who has spent many years abroad and was active in the opposition to Saddam Hussein.
Ibrahim Bahr al-Uloum, a Shia, fills the oil ministry portfolio.
After his appointment, Mr Uloum said he would seek to end fuel shortages and increase production which has been hampered by insurgent sabotage.
Mr Jaafari indicated that he was seeking a woman to fill a final deputy prime minister's position.
The announcement came as US-led forces killed six and arrested 54 suspected insurgents near the Syrian border.
In a statement, the US military said they had received intelligence suggesting that key followers of the militant leader, Abu Musab al-Zarqawi, were located in the region.
The statement said car bombs, bomb-making material and two buildings containing large weapons caches had been destroyed during the operation, near the town of al-Qaim.
The area has seen numerous attacks on the military by insurgents in recent months.