Rumsfeld said Iraq needed help to rebuild "from the rubble of tyranny"
US Congress has opened its committee hearings to consider President George W Bush's request for an extra $87 billion, mostly for military costs in Iraq and reconstruction of the country's collapsed infrastructure.
Democratic senators on the committees have wasted no time in seizing the opportunity to lambast Defence Secretary Donald Rumsfeld and other officials appearing before them.
They accused them of not giving sufficient warning to either Congress or the American people that Iraq would prove to be such a major financial commitment.
Equally, they criticised President Bush for his administration's continuing inability to verify its original justification for going to war - Iraqi possession of weapons of mass destruction.
Mr Rumsfeld, appearing before the Senate Appropriations Committee this week, said defiantly that $87bn was a small price for Americans to pay.
The cost of doing less could prove far greater for the US, he said.
"To defend freedom in the 21st Century, we need to root out terrorists," Mr Rumsfeld said.
"We need to take the battle to the terrorists and we need to help the now free people in Iraq and Afghanistan rebuild from the rubble of tyranny and claim their places as responsible members of the community of nations," he added.
But Mr Rumsfeld faced hostile questioning from Democratic committee members, led by the feisty 85-year-old senator for West Virginia, Robert Byrd.
"The American people have never been told that we are going into that country [Iraq] to build a new nation, to build a new government, to democratise the country and to democratise the Middle East," he said.
Democrats say they are concerned about Iraq's deteriorating security situation
"The people haven't been told that. They were told we were going in there because of weapons of mass destruction," he added, interrupting Mr Rumsfeld's testimony.
Republican senators remained supportive, praising US troops in Iraq and frequently chiding Democratic colleagues for "rudeness".
The head of the US-led administration in Iraq, Paul Bremer, who sat alongside the US commander in Iraq, General John Abizaid, faced similar scepticism from Democratic members of the Senate's Armed Services Committee.
No 'rosy picture'
Mr Bremer argued that $20.3 billion of the package - that they wanted earmarked for Iraq's reconstruction - was vital to establish stability.
Addressing Mr Bremer, Massachusetts senator Edward Kennedy said: "Part of the trouble for many of us is to hear the rosy picture you're describing, ambassador Bremer, and then to read about what is happening on the ground and try to understand the difference."
"You're telling us that unless we fix the infrastructure, it's going to be more and more a breeding ground for terrorists?
"Well, welcome to the fact that we're finding this out now.. and you wonder why there's concern that we don't have a plan."
Republican leaders hope to begin the debate on the Senate floor next week, despite Democratic requests for more time for hearings.
The Republicans are also fighting attempts by the Democrats to split the appropriation bill into two, allowing separate consideration of the $66bn requested by the Pentagon and the $20.3bn for Iraqi reconstruction.