President George W Bush's nominee to be the new commander of US military forces in the Middle East has called for a "new and different" approach in Iraq.
Thousands more US troops are being sent to Iraq
While providing few details, Admiral William Fallon suggested to a Senate confirmation hearing that the US should not try to achieve too much at once.
Countering Iranian influence in Iraq would be a top priority if he was given the job, he said.
His comments came amid fresh bloodshed, with 40 dead in attacks across Iraq.
More than 100 were also injured in the bomb and mortar attacks as Shia Muslims celebrated the Ashura festival.
In Washington, Adm Fallon told the Senate Armed Services Committee that the previous US strategy in Iraq was "not working".
"I believe the situation in Iraq can be turned around but time is short," he said.
"What we have been doing has not been working. [What] we have got to be doing, it seems to me, is something different."
Adm Fallon did not elaborate on what might be done differently. His spokesman, Capt William Alderson, later told the Associated Press that Adm Fallon preferred not to go into details until he had been confirmed by the full Senate.
However he did suggest that the US should not be too ambitious, at least in the short term.
"Maybe we ought to redefine the goals here a bit and do something that's more realistic in terms of getting some progress and then maybe take on the other things later," he said.
Adm Fallon, who currently heads the military in the Pacific, is poised to become the first US navy officer to head Central Command, or Centcom.
He is replacing Gen John Abizaid, who is retiring after nearly four years as Centcom chief and if confirmed would become the immediate boss of Gen David Petraeus, who was recently confirmed as the commander of US forces in Iraq.
The commander's reputation as an able diplomat is being seen as an important asset at a very sensitive time for US policy in Iraq, says the BBC's James Coomarasamy, in Washington.
If confirmed, the admiral will have to oversee the deployment of more than 20,000 US troops in a "surge" operation in Iraq.
"There are no guarantees but you can depend on me for my best effort," Adm Fallon said.
Adm Fallon also said he would seek support for efforts to counter Iranian influence in the region.
However, he said he was unaware of any contingency plans for war with Iran.
He believed Iran wanted to be able to prevent the US from operating freely in the strategically important waters off the Gulf, he added.
Separately, John Negroponte, the first US director of intelligence and a former ambassador to Iraq and to the UN, now nominee for the post of deputy secretary of state, answered questions from the Senate Foreign Relations Committee.
He backed recent tough talk towards Iran, saying Tehran was meddling in Iraq, and insisted that a diplomatic channel was already open with Syria.
"I would characterise our policy as desirous of resolving any issues we have with Iran by peaceful means," he said.
"But at the same time, we don't believe that their behaviour, such as supporting Shia extremists in Iraq, should go unchallenged."
His comments came as Democrat Senator Barack Obama expressed fears that the US would inadvertently stumble into active hostilities with Iran.