ANKARA, Turkey -- NATO will hold emergency talks on Tuesday to discuss Syria's downing of a Turkish jet fighter, but the alliance is not expected to take military action, even if it confirms Turkey's claim that the unarmed plane was attacked in international airspace.
The incident has further raised regional tensions over the conflict in Syria, where some 40 people were reported killed Sunday in new clashes between rebels and government troops.
On Sunday, U.S. Secretary of State Hillary Rodham Clinton sharply criticized Syria for downing the Turkish plane, which Turkey's Foreign Ministry called an "open and grave violation of international law" that would justify retaliation.
"The United States condemns this brazen and unacceptable act in the strongest possible terms," Clinton said in Washington. "It is yet another reflection of the Syrian authorities' callous disregard for international norms, human life, and peace and security."
Clinton said Washington will maintain close contact with Turkish officials as they determine their response, including via the U.N. Security Council. "We will work with Turkey and other partners to hold the Assad regime accountable," she said.
Turkish state media reported Sunday that the RF-4E reconnaissance plane's wreckage was found in the Mediterranean Sea at a depth of 4,265 feet (1,300 meters), but officials did not confirm the report. The two pilots remained missing.
Turkish Foreign Minister Ahmet Davutoglu said the jet was on a training flight to test Turkey's radar capabilities, not spying on Syria. He said the plane mistakenly strayed into Syrian airspace Friday, but was quickly warned to leave by Turkish authorities and was a mile (1.6 kms) inside international airspace when it was shot down.
Syria insisted Saturday that the shooting was "not an attack" and that the aircraft had violated its airspace. But Turkish authorities say Syria didn't warn the Turkish plane or send its own jets to confront it.
At the request of Turkey, NATO's governing body will meet Tuesday to discuss the incident, said Oana Lungescu, a NATO spokeswoman. The consultations were called under article 4 of NATO's founding Washington Treaty.
"Under article 4, any ally can request consultations whenever, in the opinion of any of them, their territorial integrity, political independence or security is threatened," Lungescu said. The North Atlantic Council -- the ambassadors of the 28 NATO countries -- will decide whether to respond, she said.
The last time article 4 was invoked was nine years ago -- also by Turkey -- after tensions with neighboring Iraq escalated. However, that case did not lead to the invocation of article 5, which declares that an attack against any single NATO country shall be considered as an attack against them all.
"No one should dare to test Turkey's capabilities," Davutoglu said Sunday.
Turkish Prime Minister Recep Tayyip Erdogan was expected to make a statement Tuesday and might announce some retaliatory steps.
In a telephone interview with Turkish TV news channel A Haber on Saturday, Syrian Foreign Ministry spokesman Jihad Makdissi said the downing was "not an attack.""An unidentified object entered our air space and unfortunately as a result it was brought down. It was understood only later that it was a Turkish plane," A Haber quoted Makdissi as saying. "There was no hostile act against Turkey whatsoever. It was just an act of defense for our sovereignty."
Despite some opposition leaders' calls for Western military intervention in Syria, the U.S. and allies have been hesitant to get involved in what could prove a protracted conflict, preferring the diplomatic route. Syrian allies Russia and China have shielded Syria from U.N. sanctions and stridently oppose any military intervention.
It's unlikely the downing of the Turkish plane will change those calculations, despite Ankara's appeal for the NATO meeting.
In October 1989, two Syrian MiG-21s violated Turkish air space and shot down a Turkish plane on a geographical survey mission, killing all five crew members. Syria at the time promised to severely punish the pilots, who disregarded Turkish orders not to enter Turkish airspace.
Dogu Ergil, a professor of political science at the Ankara University, told private NTV television that Turkey had repeatedly sent its jets across the Syrian border for several weeks to show its military muscle at the time.
The plane's downing drew criticism from other countries pushing Syrian President Bashar Assad to end his crack down on an increasingly armed popular uprising. Opposition activists say the conflict has killed 14,000 people, mostly civilians, over the past 15 months.
British Foreign Secretary William Hague said Sunday he was "gravely concerned by the Syrian regime's action in shooting down" the plane.
"This outrageous act underlines how far beyond accepted behavior the Syrian regime has put itself, and I condemn it wholeheartedly," Hague said in a statement. "The Assad regime should not make the mistake of believing that it can act with impunity. It will be held to account for its behavior."
Hague met last week with U.N. and Arab League special envoy Kofi Annan for talks on plans for an international summit, while British officials discussed the issue in Geneva on Saturday with members of Annan's team. Hague noted Sunday that "the UK stands ready to pursue robust action at the United Nations Security Council."
Italy's foreign minister decried the shooting down of the plane as "a further, very grave and unacceptable action by the Assad regime." In a written statement, Giulio Terzi promised that Italy will play an active role in the NATO meeting Tuesday.
Syrian activists reported violence in different parts of the country Sunday, saying nearly 40 people were killed.
The deadliest incident was in the northern town of Ariha, where a shell hit a home killing seven members of the same family, the Britain-based Syrian Observatory for Human Rights said. A video posted online showed the seven men's bodies, some badly mutilated, including one who had part of his head blown off.
Activists also reported intense shelling and clashes between rebels and troops in the eastern city of Deir el-Zour and the central city of Homs. Later in the day, Syria's state-run news agency SANA said gunmen kidnapped a pro-government Sunni cleric in the city of Deir el-Zour.
Earlier Sunday, activists said rebels captured a military base in the northern Syrian province of Aleppo, confiscating large amounts of ammunition. The Observatory said 16 government troops died in the attacks on the base near the rebel-held town of Daret Azzeh and nearby checkpoints early Sunday.
Area activist Mohammed Saeed said the rebels had removed hundreds of artillery shells from the base. Saeed added via Skype that troops retaliated with intense shelling on the area using helicopter gunships.
Syria's state-run SANA news agency, meanwhile, said gunmen from Turkey clashed with Syrian border guards in Rabiah, a region in the coastal Latakia province. SANA said several infiltrators died in the late Saturday clash, while others reportedly returned to Turkey. It said several Syrian border guards were hurt, but didn't specify how many.
Turkey denies sheltering armed Syrian rebels, although many Syrian refugees have fled to camps on the Turkish side of the border.