US President George W Bush has said early indications suggest a security operation begun in Iraq more than two months ago was "meeting expectations".
There are now almost 80,000 US and Iraqi troops in Baghdad
Mr Bush said that, while there were still horrific attacks such as Wednesday's bombings, the direction of the fight was "beginning to shift".
Thousands of extra US troops are being sent to Baghdad as part of the plan.
Meanwhile the US defence secretary met Iraq's PM to urge more progress towards national reconciliation.
Robert Gates said he wanted to emphasise that the US commitment to Iraq was not open-ended.
Also in Baghdad, US troops have started building a five-kilometre (three-mile) wall around a Sunni enclave as part of a strategy of "breaking the cycle of sectarian violence", a US spokeman said.
The wall is meant to protect the Adhamiya neighbourhood, which lies on the mainly Shia Muslim east bank of the Tigris and has been badly hit by sectarian attacks.
'Shift in direction'
President Bush said that the potential for the security plan's success could not be judged until later in the year, but the first indications were beginning to emerge.
"So far the operation is meeting expectations," he said. "There are still horrific attacks in iraq, such as the bombs in Baghdad on Wednesday, but the direction of the fight is beginning to shift."
Three US brigades had already moved into Baghdad as part of the security surge, another was preparing in Kuwait and a fifth would arrive in Kuwait next month, he said.
With three extra Iraqi troops for every American, there were now almost 80,000 in the Baghdad area, he said.
But Mr Bush said for the Iraqi government to succeed there had to be political and economic, as well as military, progress.
"It's up to the Iraqi people and the Iraq elected folks to show America and the world they're ready to do the hard work necessary to reconcile and move forward," he added.
Mr Bush's comments come a day after US Senate Majority Leader Harry Reid said that the war in Iraq was lost.