US Defence Secretary Robert Gates has asked Congress for nearly $190bn to fund the wars in Iraq and Afghanistan.
Robert Gates will urge Congress to approve the request quickly
He told a Senate committee the money would help pay for armoured vehicles to protect US troops from roadside bombs.
Democrats say they will try to use the spending request as leverage in their attempts to withdraw troops from Iraq.
Mr Gates also said he had concerns over the Pentagon's oversight of private security firms in Iraq. It follows a shooting allegedly involving a US firm.
A Pentagon spokesman said a memo had been issued to US commanders in Iraq warning them that they are responsible for overseeing private contractors.
Mr Gates has also sent a fact-finding team to Iraq to examine the issue more closely, spokesman Geoff Morrell added.
Eleven Iraqis died in the shooting two weeks ago, which provoked widespread anger. The contractor under suspicion, Blackwater USA, has said its guards reacted lawfully to an attack on a US diplomatic convoy.
Testifying to the Senate Appropriations Committee as he made the spending request, Mr Gates said he was aware of the deep concerns felt by some about the US war in Iraq.
Some of the money is needed to repair equipment already in use
"I know that Iraq and other difficult choices America faces in the war on terror will continue to be a source of friction within the Congress, between the Congress and the president and in the wider public debate," he said in prepared remarks.
But, he continued, he would like also to mention "the honour, courage and great sense of duty we have witnessed in our troops since 11 September".
Mr Gates asked for some $42bn more than the administration's initial budget request of $142bn, made in February, and an additional request for $5.3bn for armoured vehicles made in the summer.
The defence secretary told Congress that $11bn of the extra money was needed to pay for an additional 7,000 mine-resistant armoured vehicles.
A further $9bn would be spent on refurbishing equipment and technology being used in the conflicts.
He also asked for $1bn to spend on improving and consolidating US bases in Iraq and the same amount to help train and equip Iraqi security forces.
Mr Gates was expected to urge Congress to pass the request as quickly as possible "and without excessive and counterproductive restrictions", according to his prepared speech.
Mr Morrell told AFP news agency the funding request took into account the desire of Gen David Petraeus, top US commander in Iraq, to reduce troop numbers to their pre-surge levels, of about 130,000 troops, by next July.
Gen Petraeus and US Ambassador to Iraq Ryan Crocker presented a report to Congress last month in which they painted a relatively positive picture of progress on security in Iraq.