A military source close to Gen. David Petraeus told Fox News that one of the first things the general will do when he takes over in Afghanistan is to modify the rules of engagement to make it easier for U.S. troops to engage in combat with the enemy, though a Petraeus spokesman pushed back on the claim.

Troops on the ground and some military commanders have said the strict rules -- aimed at preventing civilian casualties -- have effectively forced the troops to fight with one hand tied behind their backs.

The military source who has talked with Petraeus said the general will make those changes. Other sources were not so sure, but said they wouldn't be surprised to see that happen once Petraeus takes command.

The rules, put in place by outgoing Gen. Stanley McChrystal, are classified but generally aim to limit civilian casualties by prohibiting troops from firing unless they're shot at -- or from launching bomb or artillery attacks when civilians are near the target.

Petraeus spokesman Col. Erik Gunhus disputed the claim that those rules will be revised, telling Fox News it's too soon to tell whether Petraeus would change the current rules. But he said it is one of many issues the general will take under consideration during his assessment after he's confirmed and after he takes over command in Afghanistan.

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Retired Maj. Gen. Robert Scales Jr., a Fox News military analyst, said there's no question Petraeus will have to make the changes.

"First of all, to reinforce his commitment to take care of the troops and secondly, because he realizes as does virtually everyone in Afghanistan that these rules are getting soldiers killed," he said.

Any adjustment to the rules of engagement does not mean the counterinsurgency strategy in Afghanistan will change. President Obama stressed Wednesday -- after he accepted McChrystal's resignation in the wake of a magazine article in which he and his staff were critical of the administration -- that the change-up does not represent a shift in war policy.

Rather, Defense Secretary Robert Gates said Thursday that Petraeus, currently head of U.S. Central Command and the former U.S. commander in Iraq, will have the flexibility to reconsider "the campaign plan and the approach."

At the same news conference at the Pentagon, Chairman of the Joint Chiefs of Staff Adm. Mike Mullen said Petraeus will be able to make tactical changes. But he said that does not necessarily mean changes will be made and echoed the president's insistence that the strategy stays as he prepared for a visit to the war zone.

"My message will be clear: Nothing changes about our strategy, nothing changes about the mission," Mullen said.

The issue is likely to be front and center in Senate confirmation hearings for Petraeus next week.

Fox News' Steve Centanni and Justin Fishel contributed to this report.