"I expressed concerns in the policy development phase … that this not be simply a one-dimensional surge," the three-star army general told the hearing.
 
His comments came as the US military reached another bleak milestone in Iraq on Thursday, with American deaths crossing the 3,500 mark.
 
Attacks also claimed at least 15 Iraqi lives on Thursday and Muqtada al-Sadr, an influential Iraqi Shia leader, blamed Washington for many of Iraq's problems.
 
Al-Sadr also criticised the Iraq government for failing to provide essential services to the people and helping the displaced.
 
Jury still out
 
Lute said the surge would "likely have only temporary and localised effects" unless it was accompanied by parallel efforts by the Iraqi army and civilian US government departments.
 
"The Iraqi government has taken some steps to demonstrate that it must surge, if you like, alongside of us," Lute said, while describing Iraqi progress on security as "uneven so far".
 
But he said "the bidding is still out" on whether his scepticism had been justified by events so far.
 
"Early results are mixed. Conditions on the ground are deeply complex and are likely to continue to evolve, meaning that we will need to constantly adapt," he said.
 
The creation of the "war tsar" role more than four years after the invasion has many US senators questioning whether the position signals the Bush administration is running out of ideas on how to turn the conflict around.
 
Many have questioned how effective a three-star general would be at managing a war effort from the White House and getting co-operation from four-star generals and cabinet minister.
 
They also ask whether such a position is too little too late to turn around a war most Americans no longer support.