The chief diplomats of Turkey and France have issued warnings about the seriousness of the violence that has cost thousands of lives in Syria since antigovernment protests began in March.
Turkish Foreign Minister Ahmet Davutoglu warned that the conflict in Syria risks turning into a civil war.
His French counterpart, Alain Juppe, called it "unacceptable that the Security Council remains unresponsive" to the escalating bloodshed.
The UN estimates that at least 3,500 people have died across Syria since the crackdown by President Bashar al-Assad's security forces began against antiregime protests and insurrection.
Davutoglu said a rising number of Syrian troops are defecting to the protesters' side, turning their guns on the government forces.
"There is a risk of [the confrontations] transforming into civil war," Davutoglu added.
Davutoglu was speaking in Istanbul ahead of talks with French Foreign Minister Juppe, who was in Turkey for talks on Syria ahead of a tour of Arab states.
At their joint press conference after the meeting, Juppe called on the UN Security Council to act against Assad and said the time had come to strengthen sanctions against the Syrian regime.
"I think it will be good if the Security Council comes to a decision," Juppe said. "It is not normal that in a crisis of this magnitude -- 3,500 deaths, 20,000 prisoners in Syrian prisons treated in an extremely brutal manner, tortured -- it is not acceptable that the Security Council remains unresponsive. I hope those who block all resolutions of the Security Council will become aware of the reality."
Relations between Ankara and Damascus have grown increasingly frosty
as Turkey continues to criticize Assad's response to the public dissent that has accompanied the so-called Arab Spring in the region.
Activists say that on November 17, government forces killed at least eight people, including two children, despite an Arab League ultimatum that Syria halt the bloodshed or risk sanctions.
Russia and China have blocked Western states' attempts to push through a United Nations Security Council resolution condemning Assad's regime over its crackdown.
Russia's foreign minister, Sergei Lavrov, warned similarly
on November 17 after Syrian Army defectors attacked a military base that the fighting there was beginning to look like civil war.
compiled from agency reports