Turkish Foreign Minister Ahmet Davutoglu phoned world powers on Saturday to brief them about the downing of one of Ankara's planes by Syriaas a joint search for the airmen, who were shot down over the Mediterranean, tried to locate them.
Signals from both sides suggested neither wanted a military confrontation over Friday's incident as the search focused its efforts near a Turkish province that hosts thousands of rebels fighting President Bashar al-Assad.
Given the hostility between the two former allies over Assad's 16-month-old crackdown on his opponents, the joint operation was likely to sit uneasily with both countries.
Iraq, which borders both, said the incident marked a serious escalation of the Syrian conflict, demonstrating its potential to affect other countries in the region.
"No country is immune from this spillover because of the composition of the societies, the extensions, the connections, the sectarian, ethnic dimensions," Iraqi Foreign Minister Hoshiyar Zebari said in Baghdad. "This is not an excuse to do nothing about Syria, no. But there will be an impact."
Turkey has declared it will respond decisively.
"It is not possible to cover over a thing like this. Whatever is necessary will no doubt be done," Turkish President Abdullah Gul told reporters, adding that Ankara had been in telephone contact with the Syrian authorities.
Davutoglu, Turkey's foreign minister, on Saturday evening phoned foreign ministers from the United States, Britain, France, Russia, and Iran as well as the European Union's foreign policy chief Catherine Ashton, a spokesman for the foreign ministry said. He had briefed them about Turkey's evaluation of the incident, the spokesman added.
The plane's downing showcased Syria's Russian-supplied air defenses — one of the many reasons Western powers are loathe to intervene to halt bloodshed in the country.
UN Secretary General Ban Ki-moon urged Turkey and Syria to handle the matter with restraint, using diplomatic channels.
Turkey's Deputy Prime Minister Bulent Arinc said the downed jet was a reconnaissance aircraft. Turkish media had said it was an F-4 Phantom, a fighter also used for reconnaissance.
According to a Syrian military account, the Turkish plane was flying fast and low, just one kilometer off the Syrian coast when it was shot down. It had been tracked at first as an unidentified aircraft and its Turkish origin established later.
"The navies of the two countries have established contact. Syrian naval vessels are participating along with the Turkish side in the search operation for the missing pilots," it said.
With the second biggest army in NATO, a force hardened by nearly 30 years of fighting Kurdish rebels, Turkey would be a formidable foe for a Syrian military already struggling to put down a popular uprising and an increasingly potent insurgency.
A civil war is already in full swing in Syria, where fighting or shelling engulfed parts of the cities of Aleppo, Hama, Homs, Deir al-Zor and Douma, according to the British-based Syrian Observatory for Human Rights.
"Playing with Fire"
Davutoglu met Turkey's military commanders and intelligence chief to discuss the search for the pilots and Ankara's next steps. He was due to make a statement about the incident on state TV on Sunday morning.
Prime Minister Tayyip Erdogan held two security meetings with senior officials, less than 24 hours after he convened a crisis session on Friday evening.
Separately, he called a meeting with the leaders of the country's main opposition parties for Sunday.
"Turkey will present its final stance after the incident has been fully brought to light and decisively take the necessary steps," Erdogan's office said.
Turkish newspapers were less restrained.
"They (the Syrians) will pay the price," said Vatan, while Hurriyet daily said: "He (Assad) is playing with fire."
Turkish media at first reported Erdogan on Friday as saying Syria had apologized, but the prime minister later said he could not confirm receiving such an apology.
Neither side gave any details of the joint naval search or of any communication between the two sides.
The operation was not without its ironies. Less than 50 km (30 miles) away in Turkey's southeastern Hatay province, authorities give refuge to Free Syrian Army rebels who cross daily to attack Syrian government forces. The territory also shelters over 30,000 refugees.
Turkey denies suggestions it is supplying weapons to rebels or that it is allowing third party weapons to travel across Turkish territory into rebel hands.
However, an Arab diplomat in Jeddah said on Saturday Saudi Arabia and Qatar were paying salaries to Syrian rebels, with Turkish involvement.
"The payment has been going on for months and the agreement was made on April 2 by Saudi Arabia and Qatar, with logistical organization from Turkey where some Free Syrian Army factions are based," he said, asking not to be named.
"The point of this is to encourage as many factions of the Syrian army to defect and to organize the FSA, control it and prevent any extremist organizations from joining it."
A spokesman for Saudi Arabia's foreign ministry said he was not aware of reports that the kingdom was funding Syrian rebels.
The souring of Syrian-Turkish relations has provoked concern among Turks that Syria may revive its former support for Kurdistan Workers Party (PKK) insurgents in southeastern Turkey in retaliation for Turkish backing of Syrian rebels.
"It's possible the Turks were sending jets in the area in response to an apparent escalation of the PKK's activities," Hilal Khashan, a political science professor at the American University of Beirut, told Reuters.
However, Khashan said he did not expect a harsh military reaction from Turkey. "It is under a tight leash by the United States. They don't want to start a war tomorrow."
Inside Syria, opposition activists reported heavy fighting in Deir Ezzor, an oil-producing region bordering Iraq.
The Syrian Arab Red Crescent also said one of its volunteers had been killed in the region while on first aid duty on Friday. He had been shot in the head while wearing a uniform clearly marked with the organization's emblem, it said.
Turkey fears the fighting, much of which pits majority Sunni dissidents and rebels against Assad's Alawite-dominated security forces, could unleash a flood of refugees over its own border and ignite a regional sectarian conflict.
Ankara has previously floated the possibility of setting up a safe haven or humanitarian corridor inside Syria, which would entail military intervention, but has said it would undertake no such action without U.N. Security Council approval.
Turkey has said however that Assad must go.
It was unclear why the Syrians had shot down the aircraft, which, having left a base in Malatya, was flying close to a corridor linking Turkey with Turkish forces on Northern Cyprus.
"The Syrians are clearly quite nervous and are likely to interpret any action, however innocent, as hostile," said Henri Barkey, an international relations professor at LeHigh University. "Second, reports of Turkish arms support for the insurgents also feeds the paranoia of the regime, understandably."
It was also possible the air defenses could have mistaken the aircraft for a defecting pilot, following an incident earlier in the week when a Syrian aircraft landed in Jordan.
Russia and China, Assad's strongest backers abroad, firmly oppose any outside interference in the Syrian crisis, including foreign arming or funding of insurgents, saying envoy Kofi Annan's stalled peace plan is the only way forward.
Assad's prime minister, appointed after a parliamentary election conducted last month despite the violence convulsing the country, named a new cabinet on Saturday, retaining the same interior, defense and foreign ministers.