The UN-Arab League envoy for Syria, Lakhdar Brahimi, has had talks in Turkey amid rising tensions between Ankara and Damascus.
Lakhdar Brahimi met Foreign Minister Ahmet Davutoglu to hear Turkey’s perspective on the crisis.
Several days of cross-border firing followed the killing of five Turkish civilians by Syrian shelling last week.
Earlier this week, Turkey intercepted a Syria-bound plane amid reports it had Russian-made defence equipment aboard.
Syria has dismissed the claim as a lie, challenging Turkey to show any evidence.
In Syria itself, there were reports on Saturday that rebel fighters had shot down a Syrian military jet outside Aleppo.
Footage posted online showed the burning wreckage of what appeared to be an aircraft, but the claim has not been independently verified.
Lakhdar Brahimi met Ahmet Davutoglu in Istanbul on Saturday, as did German Foreign Minister Guido Westerwelle.
“It is important that no-one pours oil on the fire. We are counting on moderation and de-escalation,” the German minister said, according to news agency AFP.
Meanwhile Turkish President Recep Tayip Erdogan told a conference in Istanbul that the UN’s failure to act in Syria gave President Bashar al-Assad the green light to kill tens or hundreds of people every day.
Turkey may not be at war with Syria, but it is now increasingly involved in its neighbor’s conflict.
President Bashar al-Assad’s government accuses Turkey, along with Saudi Arabia and Qatar, of arming the rebels.
However, Syria has said it is ready to set up a joint committee to oversee security on the border.
Its foreign ministry said it had been discussing with diplomats from Russia, a key ally, the idea of a Syrian-Turkish security committee to avoid misunderstandings at the border, which would establish a “mechanism for surveillance of the border while respecting national sovereignty”.
Lakhdar Brahimi’s visit comes a day after he met senior Saudi officials in the city of Jeddah.
Saudi Deputy Foreign Minister Prince Abdel Aziz bin Abdullah was quoted as urging “an immediate halt to the bloodshed of the Syrian people”.
However, the envoy’s visit to the region carries no immediately obvious peace plan.
He adds that UN Secretary General Ban Ki-moon has suggested Lakhdar Brahimi may head to Damascus next week if his meetings in the region go well.
Meanwhile state media in Iran, Bashar al-Assad’s key supporter in the region, say Lakhdar Brahimi is to travel to Tehran on Sunday for talks, ahead of a visit to Iraq on Monday.