US Secretary of State Hillary Clinton (L) with her Turkish counterpart, Ahmet Davutoglu
The United States and Turkey indicated on Saturday they were studying a range of measures, including a no-fly zone, as battles between Syrian rebels and President Bashar al-Assad's forces shook Aleppo and the heart of Damascus.
U.S. Secretary of State Hillary Clinton said after meeting her Turkish counterpart Ahmet Davutoglu in Istanbul that Washington and Ankara should develop detailed operational planning on ways to assist the rebels fighting to topple Assad, reports Reuters.
"Our intelligence services, our military have very important responsibilities and roles to play so we are going to be setting up a working group to do exactly that," she said.
Asked about options such as imposing a no-fly zone over rebel-held territory, Clinton said these were possibilities she and Davutoglu had agreed "need greater in-depth analysis", while indicating that no decisions were necessarily imminent.
"It is one thing to talk about all kinds of potential actions, but you cannot make reasoned decisions without doing intense analysis and operational planning," she said.
Though possible intervention appears to be a distant prospect, her remarks were nevertheless the closest Washington has come to suggesting direct military action in Syria.
No-fly zones imposed by NATO and Arab allies helped Libyan rebels overthrow Muammar Gaddafi last year. Until recently, the West had shunned the idea of repeating any Libya-style action.
Saudi Arabia and Qatar are believed to be arming Syrian rebels, while the United States and Britain have pledged to step up non-lethal assistance to Assad's opponents.
Davutoglu said it was time outside powers took decisive steps to resolve the humanitarian crisis in cities such as Aleppo, where Assad's forces have fought rebels for three weeks.
In the latest battles, tanks and troops pummeled rebels near the shattered district of Salaheddine, a former opposition stronghold that commands the main southern approach to Aleppo.
Tank fire crashed into the adjacent Saif al-Dawla neighbourhood as military jets circled over an abandoned police station held by rebels, firing missiles every few minutes.
Insurgents said they had been forced to retreat in the latest twist in relentless, see-saw battles for Salaheddine, part of a swathe of Aleppo seized by rebels last month.
Some rebels, outgunned and low on ammunition in Aleppo, have pleaded for outside military help, arguing that more weapons and a no-fly zone over areas they control near the Turkish border would give them a secure base against Assad's forces.