United States forces searching for three kidnapped soldiers say suspected al Qaeda militants holding the men are trapped in an area of farmland near Baghdad.
Backed by helicopters and using sniffer dogs, thousands of American and Iraqi troops taking part in the massive hunt have isolated towns in the so-called Triangle of Death south of the capital, where the insurgents are believed to be hiding, the military says.
Al Qaeda has warned the US military that the hunt could put the captured soldiers' lives at risk.
"The captors don't have freedom of movement; if they have the soldiers, they can't move them from where they are," said Major Kenny Mintz, an officer participating in the operation. "We're doing a deliberate search of the areas for the people responsible for the soldiers we're looking for.
"Right now our focus is on searching for the missing soldiers and we're trying to isolate the areas where we think they could be," Mintz was quoted as saying in the statement.
The soldiers, part of a larger unit sent to intercept roadside bombs in a Sunni Arab militant stronghold, went missing after a coordinated ambush on Saturday in which four other US soldiers and an Iraqi army translator were killed.
The search is in a terrain of orchards and canals near the town of Mahmudiya, where suspected al Qaeda militants abducted two US soldiers in June. The soldiers' badly mutilated bodies were found days later.
The US military said it had detained 11 people and conducted "tactical questionings" since the search began.
The al Qaeda-led organisation known as Islamic State in Iraq has mocked the US forces' efforts, saying "you are only tiring yourself." The Sunni Islamist group has not given any proof the soldiers are still alive.
War Czar
In Washington, US President George W Bush has named Army Lt Gen Douglas Lute as White House "war czar" for Iraq and Afghanistan to coordinate policy among sometimes competing agencies and to try to implement Bush's war strategy.
If confirmed by the Senate, Lute, 54, will take on the high-profile job against a backdrop of rising Democratic criticism of the unpopular war and the failure so far of a troop buildup to halt violence.
Bush is deploying 30,000 more troops in Iraq in a last-ditch effort to stop a slide into all-out civil war between majority Shi'ites and Sunni Arabs.
Bush, who has called al Qaeda "public enemy number one" in Iraq, is under growing pressure from Democrats to set a timetable for withdrawal of troops. More than 3,300 US soldiers have been killed since the 2003 invasion to oust Saddam Hussein.
Some moderate Republicans have also suggested they will desert Bush unless he shows political and military progress by September, when the American commander in Iraq is due to present an assessment report.
Constitutional reform
In Baghdad, a committee set up to reform Iraq's constitution says it will send its draft to parliament next week.
Sunni Arabs, who make up the backbone of the insurgency, say the constitution in its current form cedes too much power to majority Shi'ites and ethnic Kurds.
Other legislation that Bush is pressing Iraq to pass includes laws to share Iraq's vast oil wealth and to end a ban on former members of Saddam's party holding public office.
In Washington, White House spokesman Gordon Johndroe welcomed the move, but said "There is more work to be done, but this step will help in the process of bringing all Iraqis together to help build a stable, secure and unified democracy."
Resistance is expected in parliament, especially from Shi'ites
virulently opposed to former Baath members returning to positions
of influence and from non-Arab Kurds who resist the wording on the
Arab identity of Iraq.
