By Nick Childs
BBC News, Pentagon
A senior retired US army general tasked with reviewing the security situation in Iraq has begun his mission, the Pentagon has confirmed.
US troops levels in Iraq are at the highest ever
General Gary Luck's review will look in particular at the development of Iraq's security forces - key to the Americans' eventual departure from the country.
The highly-respected four-star general was asked by the US defence secretary to carry out the assessment.
General Luck and his team are expected to be in Iraq for about two weeks.
The mission comes at a critical time and its particular focus, the development of the Iraqi security forces, is crucial to any US exit strategy from Iraq.
There remain concerns about the performance of the Iraqis, especially as they have been increasingly targeted by insurgents.
Indeed, one US defence official said it is estimated that 1,200 Iraqi personnel have been killed in all.
Still, another senior official rejected the idea that the Luck mission is about US disengagement. It is about winning, he said.
The Pentagon spokesman also refused to put a timeframe on when US force levels in Iraq might start to go down.
There are currently 150,000 US troops in Iraq, the highest number there has ever been.