NATO said it would meet to discuss member state Turkey's accusation that Syria shot down one of its warplanes in international airspace and not inside its own territory, as Damascus claims.
NATO said it would hold an emergency meeting on Tuesday following a request from Turkey that invoked Article Four of the alliance's founding treaty, which covers threats to member states' security.
Turkey’s cabinet was due to meet on Monday to discuss Friday’s incident, which lent a more threatening international dimension to the 16-month-old uprising against Syrian President Bashar al-Assad.
Turkey has already acknowledged that its fighter jet might at some point have entered Syrian airspace. But after an initially cautious response, Ankara toughened its rhetoric on Sunday.
Turkish Foreign Minister Ahmet Davutoglu told Turkey's TRT television that at the time it was shot down, their plane was in international airspace, 13 nautical miles from Syria.
Syria had given no warning before opening fire, he added.
The fighter had been on an unarmed training mission to carry out a radar system test, and both pilots are still missing, according to Syrian officials.
Syria has officially acknowledged shooting down the F-4 phantom jet after it violated its airspace, but insists it only identified it as a Turkish fighter after the fact.
"What happened was an accident and not an assault as some like to say," Syrian foreign ministry spokesman Jihad Makdissi told the Al-Watan pro-government daily on Sunday.
“Turkish Jet, which was downed by Syrian forces, had violated Syrian airspace.” the Syrian Foreign Ministry spokesman Jihad Maqdissi said Monday.
He added that Syria “could take positive steps if the Turkish government takes similar steps.”
Syrian FM spokesman also indicated “The rescue efforts are underway with the coordination of all sides. We found the wreckage of the jet and Turkey was informed about it.”