After a five-month pacification effort, security forces in Baghdad have full control of about 40 per cent of the city, says the U.S.'s top general in Iraq.

Gen David Petraeus made the remarks Saturday as he announced that the U.S. has launched a new offensive operation targeting al Qaeda strongholds around Baghdad's southern outskirts.

The major offensive began in the past 24 hours and is an attempt to stamp out al Qaeda's barrage of car bombings, he said.

Troops will focus on areas al Qaeda is thought to be using as bases for its attacks.

Petraeus told reporters the deployment of 30,000 additional troops -- bringing total troop numbers in Iraq to 155,000 -- made the new campaign possible. He said with soldiers are being sent for the first time into a number of al Qaeda "sanctuaries."

"Our job now, frankly, along with the job of our Iraqi counterparts ... is to do everything that we can with the additional forces that we have."

He noted that he would like to have even more troops, but knows he will have to make do with the current numbers.

Petraeus said he believes the new offensive -- of which he gave few details -- will help the military make some progress. The war is in its fifth year and more than 3,500 U.S. military personnel have been killed -- many as the result of suicide bombings.

U.S. Defence Secretary Robert Gates -- who is currently on a surprise visit to Iraq -- and his top commanders face mounting pressure at home to show progress in the conflict, so that troops can begin coming home.

The Iraqis' failure to meet a number of benchmarks has added to the frustration, said U.S. Ambassador Ryan Crocker.

"We are pressing hard on those," he said, referring to oil sharing legislation and political reconciliation between various factions -- both objectives set by the U.S.

"The Iraqi government is pressing itself. Progress has been frustratingly slow. We will see where we are by September."

The top U.S. commander in the Middle East, Adm. William Fallon and John Negroponte, the second State Department official, both brought the same message to the war-torn nation in the last week.

The meeting's results

Aides to al-Maliki told The Associated Press that Saturday's talks with Gates were difficult.

The prime minister, a Shiite, strongly objected to a new U.S. policy of arming Sunni Muslim militants to fight al Qaeda.

Gates reported told al-Maliki that a new law to share oil revenues among all Iraqis must be finished by September when the defense secretary reports to Congress on progress in Iraq.

Gates also met with President Jalal Talabani, a Kurd, and said he was concerned about Iraq's security situation spiralling out of control.

AP said the Iraqi officials only agreed to discuss the talks if they weren't quoted by name as they weren't authorized to provide details. The sources said they were briefed on the talks by those officials who attended the meeting.

With files from the Associated Press