President Bush's choice for the new army chief of staff has denied that current US policy on Iraq has failed.
General Casey faced a hostile committee hearing
General George Casey, the top US commander in Iraq for the last two years, faced tough questioning at his Senate confirmation hearing.
But he disputed Republican Senator John McCain's suggestion he had painted an overly "rosy" picture of events.
"I do not agree that we have a failed policy," he told the Senate Armed Services Committee.
President Bush plans to send 21,500 more US soldiers to Iraq to help stem the conflict.
But Gen Casey said security in the capital, Baghdad, could be improved without such an influx of extra troops.
"I do believe the job in Baghdad as it's designed now can be done with less than that," he told senators.
"But having the other three brigades on a deployment cycle gives General Petraeus [his successor] great flexibility," he said.
'Wrath of senators'
The BBC's James Coomarasamy, in Washington, says the atmosphere at the hearing was hostile.
General Casey felt the wrath of senators who feel that they and the country have been deceived by their military leaders, our correspondent says.
Time and again, senators quoted back at the general comments he has made before the committee during his two-and-a-half years in charge of US operations in Iraq.
There is a real chance that the general will not be confirmed as the army's next chief of staff by a Congress seeking to pass judgement on past failures in Iraq, our correspondent adds.
On Wednesday, the president's nominee to be the new commander of US military forces in the Middle East, Admiral William Fallon, called for a "new and different" approach in Iraq.
He told the armed services committee that the previous US strategy in Iraq was "not working" and that goals should be more modest.