VILNIUS, Lithuania -- A senior State Department official said Friday that the military strike the United States is planning would not fundamentally alter the military balance in Syria and would likely be followed by a prolonged "war of attrition" among the Syrian combatants.
'I don't expect huge, huge change on the day after on the ground," said the official, who is traveling with Secretary of State John Kerry to a meeting in Vilnius with European Union foreign ministers on the Middle East. "That grinding war of attrition will continue and the regime's manpower shortages will continue to grow, but I would not expect a breakthrough on the ground."
The official's comments came amid a debate in Washington over how hard a blow the U.S.-led military attack should deliver if Congress authorizes action, and to what extent an attack should be aimed at degrading the military forces loyal to President Bashar Assad in addition to deterring future chemical attacks.
Sen. John McCain, R-Ariz., has argued that one of the goals of the strike should be to tip the balance in the civil war more toward the opposition, by attacking the government's air force and other weapons at its disposal that can deliver conventional as well as chemical arms. But that has spurred fears of "mission creep" on the part of other lawmakers, who fear that an attack would set off a chain of escalation in which Mr. Assad would retaliate, and the United States and its allies would be forced to respond.
There has been a parallel debate between U.S. officials who have met with the Syrian opposition over the past two weeks to discuss the basic parameters of the strike. "We have been very explicit to the Syrian opposition that any military action that we might take in response to the chemical weapons attack is going to be limited and very focused, solely on re-establishing the deterrence," said the official, who requested anonymity as per diplomatic protocol.
"Do they all welcome that?" he said. "No, some would like us to do more than that. They will be disappointed, therefore."
Even if the strikes are somewhat limited, the official asserted, they would discourage the Assad government from again using chemical weapons and that, in any case, the condition of Syrian forces would weaken over time.
But he suggested that the push to improve the rebels' fortunes on the battlefield, and ultimately foster the condition for a possible political settlement, would depend more on increasing efforts to arm the opposition and improve its ability to govern the area it has captured.
The official introduced some of the arguments U.S. officials are expected to make to their European counterparts during Mr. Kerry's four-day trip. He asserted that the failure to act militarily presented graver risks than a limited military intervention.
Syrian civilians, fearful that the Assad government would strike again with chemical weapons, would continue to flood into Lebanon, Jordan and Iraq, he said. Moderate elements of the Syrian opposition would be weakened.
Extremists who have argued that the United States cares only about Israel, and that it is foolhardy to rely on assurances from the White House, he said, would get a "boost."
Mr. Kerry's trip was initially designed mainly to support the peace talks between Israel and the Palestinians, which resumed after nearly three years.