US President George W Bush has defended his decision to commit thousands more troops to the Iraqi capital, Baghdad, in a drive to end sectarian violence.
Mr Bush said the US had to prevent the violence in Iraq worsening
Speaking in a TV interview, he said that the US had to tackle the violence or it would spiral out of control.
Too many people had died "as a result of Shias killing Sunnis and Sunnis killing Shias", he said.
His comments came after 70 people were killed and scores more injured in a double bombing at a Baghdad university.
A car bomb blew up outside Mustansiriyah University, in a predominantly Shia area. A suicide bomber then targeted students, mainly female, as they fled the scene.
Earlier on Tuesday, the UN said more than 34,400 Iraqis had died in 2006 in violence across the country, more than three times the Iraqi government's estimate.
'Spiral out of control'
Last week Mr Bush announced the deployment of an additional 21,500 US troops to Iraq, the majority of whom will go to Baghdad.
His plan has drawn tough domestic criticism, but speaking in an interview on the PBS programme NewsHour with Jim Lehrer, Mr Bush said that he believed he had made the right decision.
"If the United States does not step up to help the Iraqis secure Baghdad... if we don't crack this now the violence will spiral out of control," he said.
He blamed al-Qaeda for triggering the sectarian violence, saying it was "important for the American people to understand it is al-Qaeda that is doing a lot of these spectacular bombings".
And he emphasised the consequences of failure in Iraq.
"This is a war, part of a broader war, and if we fail in Iraq there's a better likelihood that the enemy comes and hurts us here," he said.
While "pleased" with the trials of Saddam Hussein and two of his aides, he also expressed concern about the way their executions were conducted.
"I was disappointed and felt like they fumbled, particularly the Saddam Hussein execution."
He said the manner of the execution made it harder for him to convince Americans that Iraq had a serious government that wanted to unify the country.
There has been widespread international concern over the former Iraqi leader's execution, who was seen being taunted just prior to his death.
His half-brother, Barzan Ibrahim, was accidentally decapitated when he was hanged two weeks later.