Limited military strikes against Syria favored by President Barack Obama may have a psychological effect but little practical impact on the Damascus regime's firepower, experts said Wednesday.

Vowing to avoid large-scale, open-ended action, Obama has proposed a "shot across the bow" in a bid to punish President Bashar al-Assad for allegedly resorting to chemical weapons.

"In a shot across the bow, you don't hit anything. It's a demonstration of resolve," said Michael Eisenstadt, a former US military adviser.

"If that's the way he sees it, then it really doesn't matter whether it's 50 or 100 (Tomahawk missiles)," he said. "It's just the very fact that you're doing it, that that should be enough."

The Obama administration is believed to be contemplating a series of cruise missile strikes that would likely hit command posts, airfields and units linked to chemical attacks.

The Pentagon says the goal of punitive strikes would be to "deter" Assad from using chemical weapons again and "degrade" his army's ability to launch the lethal agents.

But even after a wave of missile strikes launched from warships and possibly from B-2 bombers, Assad's forces would still have artillery capable of unleashing lethal sarin gas or other chemical agents, analysts said.

"If we really wanted a military effect, what we could do is deprive the Assad regime of its most efficient delivery mechanism (for chemical weapons) -- artillery," said Jeffrey Martini, a Middle East analyst at the RAND Corporation think tank.

"That operation would look a lot different from the one that it seems the administration in envisioning," he told AFP.

The military action that Congress is now debating appears to be about "psychological" effects and not "military effectiveness," he said.

Leaks and a political debate in Washington over the merits of intervention has removed any element of surprise, allowing the Syrian regime time to disperse troops and equipment that could be targeted in any action, experts said.

"That clearly makes it more difficult to accomplish a certain minimal amount of damage on the Syrians," said Eisenstadt, senior fellow at the Washington Institute for Near East Policy.

The US military's top officer, General Martin Dempsey, told lawmakers Tuesday there was no doubt American forces would inflict damage on Syria's chemical weapons capacity and would be using an extensive list of targets.

"I'm confident in the capabilities we can bring to bear to deter and degrade," said Dempsey, the chairman of the Joint Chiefs of Staff.

"And it won't surprise you to know that we will have not only an initial target set but subsequent target sets should they become necessary," said the four-star general, implying the operation could last beyond a single day.

The administration hopes to "alter Assad's calculus," said Steven Pifer of the Brookings Institution, but there are no guarantees.

"Two weeks ago, all evidence suggests that Assad felt he could use chemical weapons with impunity," he said.

"A punitive military strike would demonstrate that such action has costs and might -- might -- affect his future calculation."

With Congress pushing Obama to impose explicit restrictions on the operation, including prohibiting any "boots on the ground," the constraints could undermine the intended psychological impact of the missile strikes, according to Eisenstadt.

"Probably the main way Assad will respond will be to use chemical weapons again, but probably on a much lower level, similar to the way he did previously," he said.

"In order to put the administration in the horns of a dilemma."

Obama would then have to consider a second wave of strikes, opening himself up to criticism that he is dragging the United States into a quagmire -- despite promising to avoid a repeat of the Iraq debacle.

In that scenario, if the United States chose not to launch further action, "Assad will be able to claim that he is unbroken, unbowed and defiant," Eisenstadt said.

"And it puts us in a very difficult situation."