New Iraqi security checkpoints have been set up across the city and
thousands of US soldiers have begun to be deployed as the operation begins.
Hoda Abdel-Hamid, Al Jazeera's correspondent in Iraq, says Iraqis hope the operation will help stem the brutal sectarian violence that has gripped the capital.
"From the streets the anger is growing and Iraqis want to see good results."
A new joint US-Iraqi command centre is to take control of the latest security operation.
The Baghdad Operation Command will officially takeover on Monday and a massive security offensive will follow soon after, US colonel Douglass Heckman, a senior military adviser, said.
The new command is part of plans by George Bush, the US president, for an offensive to end Baghdad's sectarian violence.
"It's going to be an operation unlike anything this city has seen. It's a multiple order magnitude of difference ... a couple hundred per cent," Heckman said.
Heckman said US and Iraqi reinforcements were already in place for a neighbourhood-by-neighbourhood sweep of the city.
Informed sources said about 8,000 US soldiers were expected to transfer into Baghdad or nearby regions, joining about 15,000 US soldiers already in the capital and its suburbs.
"Maybe it'll work. Maybe it won't. It's gonna be much more than this city has ever seen and it's gonna be a rolling surge," Heckman said.
Iraqis have said they will take the lead in the operation, but US officers say they would retain oversight, at least initially.
American and Iraqi commanders are pulling together a force of about 90,000 troops, for what many see as a last-chance drive to curb the sectarian violence that has turned the city of six million people into a battlefield.
The new joint command will be headed by Iraqi Lieutenant-General Abboud Gambar.
Gambar was chosen by the US military, which rejected the choice of Nuri al-Maliki, the Iraqi prime minister, of Lieutenant-General Mohan al-Freiji.
US Colonel Chip Lewis said: "It'll be a steadily increasing amount of pressure brought to bear on the insurgents and the militias and the criminals."
Lewis said the joint command, which would control all Iraqi security forces in Baghdad, would include embedded US service members but the overall operation would be run by Gambar.
Embedded American troops will not take orders from Iraqi commanders.
Gambar will have two deputies, a Shia and a Sunni, one on either side of the Tigris river that curls through the centre of the Iraqi capital.
The joint command comes into operation two days after 135 people were killed and more than 300 wounded in the worst single bombing in Baghdad since the US-led invasion in 2003.
Mortar attacks also killed 15 others in a Sunni neighbourhood of Baghdad on Sunday.
More than 20 people were reported killed elsewhere in the Iraqi capital in bombings and drive-by shootings and police found 42 bodies, believed to be victims of sectarian execution-style killings.