US Secretary of State Condoleezza Rice has again defended the war in Iraq, saying the investment in US lives and dollars will be "worth it".
Rice said the Middle East would benefit from the sacrifice
Ms Rice said a lot had been sacrificed for Iraq but success would change the entire Middle East.
She was speaking soon after eight US marines were charged over the deaths of 24 Iraq civilians in Haditha last year.
President Bush said for the first time this week that the US was not winning the war, but was not losing it either.
In the latest violence on Friday, three US marines and a sailor died from their wounds during fighting in Anbar province, the US military said.
The BBC's Justin Webb in Washington says that in her interview with Associated Press news agency, Ms Rice made it plain that she still believed Iraq should be seen as the centrepiece of US-Middle East policy.
She acknowledged that a lot had been sacrificed for Iraq and a lot invested in the country but that it would be worthwhile.
Lt Col Jeffrey R Chessani: Violation of a lawful order; dereliction
Sgt Sanick P Dela Cruz: Unpremeditated murder; false official statement
1st Lt Andrew A Grayson: Dereliction; false official statement; obstructing justice
Capt Lucas M McConnell: Dereliction
Lance Cpl Justin L Sharratt: Unpremeditated murder
Capt Randy W Stone: Violation of a lawful order; dereliction
Lance Cpl Stephen B Tatum: Unpremeditated murder; negligent homicide; assault
Staff Sgt Frank D Wuterich: Unpremeditated murder; soliciting another to commit an offence; false official statement
She said: "There have been plenty of markers that show that this is a country that is worth the investment, because once it emerges as a country that is a stabilising factor, you will have a very different kind of Middle East."
President Bush faces continuing pressure in Congress to find a new strategy for the war.
In recent months, many of those advising the White House, including UK Prime Minister Tony Blair and the Iraq Study Group, have suggested that the Arab-Israeli conflict is the real key to peace in the region.
Ms Rice was speaking after the announcement of the Haditha charges, which our correspondent says is likely to add to a sense of national gloom over Iraq.
Haditha is now the biggest US criminal case involving civilian deaths since the invasion of Iraq in 2003.
Four of the eight marines charged are accused of unpremeditated murder and the four others are charged with attempting to cover up the incident.
The US military initially said the civilians died in unrest. If found guilty of second-degree murder, the marines could face life imprisonment.
Lawyers for the marines accused of murder will strongly defend their clients' actions.
The BBC's Nick Miles in Washington says the case has provoked debate about the training and leadership of US troops in Iraq.
Wuterich was the marine squad leader at the time of the killings
The defence team says a group of marines from Kilo Company in the First Marine Division were engaged in a furious battle on 19 November 2005 in Haditha after a roadside bomb exploded, killing one marine and injuring two others.
It is known that five unarmed men were shot dead in a car when they approached the scene in a taxi and others, including women and children, died in three houses over the next few hours.
Iraqi Prime Minister Nouri Maliki has called the deaths a "terrible crime".
The BBC's Peter Greste in Baghdad says the response in Iraq to the charges has been muted.
He says there is a perception that Iraqi civilians die every day, either directly or indirectly as a result of US military action, and that this case stands out only in the numbers involved.
According to the charge sheets, Staff Sgt Frank D Wuterich ordered his men to "shoot first and ask questions later" when they entered a house.
There was no full US investigation into what happened until three months later when video footage that was taken by a local human rights activist of the aftermath reached Time Magazine.
Once its report showed flaws in the initial marine statement, an investigation began.
The Haditha inquiry is just one of a number the US military has been conducting into incidents of alleged unlawful killings by US forces in Iraq.
Haditha, 96km (60 miles) north of Baghdad, is the furthest in a string of settlements up the Euphrates that have been prominent in the Sunni insurgency.