By Phil Stewart
WASHINGTON, Sept 5 (Reuters) - It would hardly be a surprise to Syrian President Bashar al-Assad or his military if American missiles start hitting Syria soon.
With weeks to prepare for an attack, Assad might benefit in some ways from the delay in any strike caused by President Barack Obama's decision to seek approval from a divided U.S. Congress.
U.S. officials and defense experts say Assad's forces cannot take enough targets out of reach to blunt the U.S. military mission, especially since it is billed as having very limited objectives.
Obama is calling for a limited military strike in response to a chemical weapons attack on civilians blamed by the United States on Assad's forces.
Fixed targets, for example, cannot be protected no matter how much time elapses. "A building can't be moved, nor hid," one U.S. official said, speaking on condition of anonymity.
Other fixed targets could include airfields, although not any storage facilities with chemical weapons in them.
Defense analyst Anthony Cordesman of the Center for Strategic and International Studies think tank said if successful, hitting fixed targets would eliminate key assets to Assad that "can't easily be replaced, like command and control facilities, major headquarters."
"These are lasting targets," Cordesman said.
It is still unclear when any U.S. attack on Syria will happen but Assad already has had ample time to try to get ready. U.S. officials have been openly discussing the possibility of hitting Syria since shortly after the Aug. 21 chemical weapons attack near Damascus.
Even if Congress approves military action, a final vote would be unlikely before the middle of next week.
A second U.S. official, also speaking on condition of anonymity, acknowledged that the delay added "complexities" to the planning efforts.
"It may change target sets," the official said. "We'll continue to refine our targeting options to conditions on the ground."
Assad has already moved some military equipment and personnel to civilian areas and put soldiers whose loyalty to Assad is in doubt in military sites as human shields against any Western strikes, the Istanbul-based Syrian opposition has said.
It cited movement of rockets, Scud missiles and launches, as well as soldiers to locations including schools, university dormitories and government buildings inside cities.
That could complicate the ability of the United States to reach some targets.
General Martin Dempsey, chairman of the U.S. military's Joint Chiefs of Staff, acknowledged publicly to Congress that Obama has ordered the military to develop plans that keep a lid on collateral damage - civilian deaths and damage to civilian infrastructure.
"Though they are in fact moving resources around - and in some cases placing prisoners and others in places that they believe we might target - at this point our intelligence is keeping up with that movement," Dempsey, the top U.S. military officer, told lawmakers on Wednesday.
WAIT FOR MONTH?
The question of whether losing the element of surprise makes a difference militarily became a bone of contention in the debate over congressional backing for Obama's attack plan.
Senator John McCain, one of the Republicans who has pushed hardest for military action in Syria, said this week he was "astounded" when Obama said the military had advised him that an attack would still be effective in a month's time.
"When you tell the enemy you are going to attack, they are obviously going to disperse and make it harder," McCain said in Congress on Tuesday.
"It's ridiculous to think that it's not wise from a pure military standpoint not to warn the enemy that you're gonna attack," McCain said.
The Obama administration says the planned attack is designed to strike a particular balance - being strong enough to deter Assad from using chemical weapons in the future while also degrading his ability to do so.
But the Obama administration has said any attack would not be designed to topple Assad or necessarily shift the momentum in Syria's civil war to the detriment of government forces.
U.S. objectives include targets directly linked to the Syrian military's ability to use chemical weapons, as well as missiles and rockets that can deliver them, Dempsey said.
Air defenses that could be used to protect chemical weapons sites are also potential targets, Dempsey said.
"That target package is still being refined as I sit here with you," Dempsey told lawmakers.
Despite the stated objective of deterring Assad, the U.S. military cannot guarantee its strikes will prevent Assad from using chemical weapons in the future.
Even the objective to degrade - a military term that means "diminish" - his capabilities is vague. There has been no clear, public objective offered by the United States on how much it must damage Assad's capabilities. (Additional reporting by David Alexander; Editing by Alistair Bell and Will Dunham)