WASHINGTON -- The Obama Administration is weighing its options for more direct involvement in the Syrian civil war if the rebels can wrest enough control to create a safe haven for themselves, U.S. officials said.
Secretary of State Hillary Clinton said it's only a matter of time before the rebels have enough territory and organization to create such areas.
"More and more territory is being taken," Mrs. Clinton said this week. "It will eventually result in a safe haven inside Syria, which will then provide a base for further actions by the opposition."
Officials are starting to brainstorm how a safe zone might allow Washington to step up its assistance, which has been limited to humanitarian aid and nonlethal equipment such as medical supplies and communications gear.
For now, U.S. officials are standing by their assertion that they won't provide arms to Syrian forces fighting against President Bashar Assad's troops nor push for a no-fly zone over rebel-controlled areas.
In Syria Thursday, Damascus and Aleppo came under shelling as troops loyal to Assad stepped up efforts to crush threats to the government's two main power centers.
Anti-government activists said the army mustered soldiers, tanks, and support vehicles on the southern outskirts of Aleppo, the country's commercial capital, for an assault on rebel fighters there.
But the Syrian government appeared to be holding back on what would amount to a military invasion of Aleppo until it amassed a larger contingent of forces.
As tensions grew in Aleppo, Turkey's prime minister said Syrian forces had abandoned territories close to the Turkish border that have since been occupied by Kurdish militants hostile to Turkey.
Turkish Prime Minister Recep Tayyip Erdogan said his country's military would "take whatever steps are necessary against terrorism" in these areas, foreshadowing possible Turkish military incursions into Syria, similar to Turkey's incursions into areas of northern Iraq where Kurdish militants have sought sanctuary.