A command centre for a joint US-Iraqi offensive aimed at restoring security in Baghdad is about to go into operation, US military officials say.
The US currently has 132,000 soldiers in Iraq and is sending more
The centre begins work amid escalating violence that saw 130 people die in a Baghdad suicide bombing at the weekend.
But it is not clear when the much-heralded security push will begin.
The worsening situation has prompted Iraq's Sunni Vice-President to call on the US to speed up its promised deployment of extra troops to Baghdad.
Tariq Hashimi, one of the country's two vice-presidents and the country's most senior Sunni politician, told the BBC that previous efforts to stem the violence had failed because they involved too few combat troops.
"I...would like to see the troops that we've been promised very soon," Mr Hashimi said, warning that if that did not happen, the situation could deteriorate even further.
He was also scathing about the Iraqi government's own response to the violence, saying it was slow and unprofessional, while he blamed the increase in attacks on Iran, arguing that the recent bombings were so large a government had to be involved.
Despite Mr Hashimi's call for a speedy deployment, it is still likely to be several months before the US and Iraqi governments have the extra troops in place, reports the BBC's Andrew North from Baghdad.
The new command centre is being headed by an Iraqi officer, Gen Abboud Gambar, a Shia who fought US forces in the 1991 Gulf War.
The offensive will involve US and Iraqi forces sweeping Baghdad neighbourhoods for militants and illegally held weapons.
The Iraqi government says it will announce guidelines for the new plan in the coming days.
It will be the third attempt at pacifying the capital since Iraqi Prime Minister Nouri Maliki took power in May.
However, violence has continued to escalate in Baghdad. Saturday's attack in the Sadriya district of Baghdad was the deadliest single bombing since the US-led invasion of 2003.
An interior ministry official told Associated Press news agency about 1,000 Iraqi civilians, security personnel and militants had died in the past week alone.
And on Monday, the US military reported that an American soldier had been killed in the volatile Diyala province.
The BBC's Mike Wooldridge in Baghdad says the flaw in previous attempted crackdowns in the capital has been that violence has sometimes been reduced only to return.
Saturday's bombing obliterated a market packed with shoppers
But Col Doug Heckman, an adviser to the Iraqi army, said the new operation would be "a multiple order magnitude of difference" compared with previous offensives.
"It's going to be much more than this city has ever seen and it's going to be a rolling surge," he added.
Another US officer, Col Chip Lewis told reporters: "It will be a steadily increasing amount of pressure brought to bear on the insurgents and the militias and the criminals."
It is unclear how many US and Iraqi soldiers will take part in the offensive.
US President George W Bush has announced he is sending an extra 21,500 troops to Iraq - most of them earmarked for the Baghdad operation.
Col Heckman said he expected to see "concrete results" in the next six months.
On Sunday the US military for the first time said that four US helicopters lost in Iraq in recent weeks appeared to have been downed by ground fire. Three army helicopters and a private aircraft have come down since 20 January, with the loss of 20 US lives.
Correspondents say the recent incidents have raised new questions about whether insurgents are using more sophisticated weapons.