Cheney is among the administration's hardliners
US Vice President Dick Cheney has mounted a spirited defence of Washington's war on terrorism, vowing to destroy militant groups and their sponsors worldwide.
"The terrorists have sustained heavy losses, they will sustain more," said Mr Cheney - one of the administration's foreign policy hardliners.
Mr Cheney's speech on Friday was part of a White House public relations offensive aimed at countering growing criticism of US policy in Iraq.
President Bush's opinion poll ratings have slumped amid rising US casualties in Iraq and the failure to find any weapons of mass destruction there.
The campaign also comes as the US Congress begins to debate Mr Bush's request for an extra $87bn in emergency funding to rebuild Iraq and Afghanistan.
Mr Cheney said that after two years of investigating al-Qaeda, the administration had no doubt that terror groups had been trying to acquired weapons of mass destruction.
Speaking at the Heritage Foundation, a conservative Washington think-tank, he said the US had to do everything to prevent what he called "the ultimate nightmare".
He said traditional doctrines of deterrence and containment did not work against American's new enemies.
"We have to destroy terrorists before they attack us," Mr Cheney said.
He also reaffirmed the "Bush doctrine", which states that any government that helps terror groups will be "held to account".
Chronic insecurity still plagues the people of Iraq
He said the US administration was committed to multilateral action - but would not give other powers a veto.
"We are in charge of our own security," he said.
Mr Cheney vigorously defended US policy in Iraq, saying that Saddam Hussein would still be in power if opponents of the war had prevailed.
He said Iraq was a better place now and "an example of freedom for all the Middle-East".
However, the US administration heard more bad news from Iraq on Friday, including the deaths of two US servicemen in an ambush in Baghdad.
The White House offensive was kicked off on Wednesday by Mr Bush's National Security Adviser, Condoleezza Rice.
She said new evidence uncovered by weapons inspectors proved Iraq had posed a serious threat and that the invasion was justified.
Bush: US work in Iraq "essential to our own security"
Ms Rice said the credibility of the United Nations would have been "in tatters" if the US had not acted.
On Thursday Mr Bush described Iraq as the "central front" in the US-led war on terror.
"America must not forget the lessons of 11 September," said in a speech to National Guard members in New Hampshire.
"America cannot retreat from our responsibilities and hope for the best. There is only one option - we must fight this war until our work is done."