That fear of escalation between Syria and Turkey grew stronger today, as Turkish Prime Minister Recep Tayyip Erdogan described Syria as “a clear and imminent threat,” promising to retaliate for a downed Turkish jet, and warning the Syrians about approaching the Turkish border.

In his most outspoken criticism of the Damascus regime, Erdogan vowed to retaliate against the “heinous act” and promised a change of military attitude to any Syrian officer approaching the common border.

“The rules of engagement of the Turkish Armed Forces have changed given this new development,” Prime Minister Recep Tayyip Erdogan told parliament following the shooting down of F-4 Phantom jet Friday. The two pilots are still missing.

Any risk posed by Syria on the Turkish border will be “considered a threat and treated as a military target,” he said in a jam-packed room of lawmakers who frequently interrupted the address with applause.

Erdogan said his government would retaliate “with determination” and take what he called the “necessary steps by determining the time, place and method by itself”.

Erdogan is known to have a hot temper, and this was a political speech. But coming several days after the event, it certainly sounds like a new policy for Turkey, and one that risks a regional conflict.

Moreover, NATO provided some backing to Turkey in the dispute, as secretary general Anders Fogh Rasmussen described the shooting down of the plane by Syrian forces as unacceptable.

Turkey now claims that the unarmed jet was shot down over international waters, and not Syrian airspace (though the jet was in Syrian airspace for a short time). In addition, Erdogan said that Syria had violated Turkish airspace on 5 separate occasions since the beginning of the year (out of 114 total violations from other countries), and that Turkey always delivered a warning to the planes; Syria delivered no warning, according to Erdogan, before shooting down the jet.

Meanwhile, this situation over the jet could be a proxy fight about Turkish support for the rebel opposition:

The onetime ragtag militias of the Syrian opposition are developing into a more effective fighting force with the help of an increasingly sophisticated network of activists here in southern Turkey that is smuggling crucial supplies across the border, including weapons, communications gear, field hospitals and even salaries for soldiers who defect.

The network is emerging at a time of heightened tensions with Turkey and amid reports of multiple defections of high-ranking officers from the Syrian Army, many of whom are now helping the opposition. Turkey will sit down on Tuesday with its NATO allies to discuss a response to the downing of one of its warplanes by Syrian gunners, while on Monday Turkey reported that a general and two colonels had defected from Syria on Sunday, bringing the total to more than a dozen.

The undertaking by the opposition here constitutes more than just ferrying much-needed supplies. The larger, more elusive goal is to create cohesion and cooperation between the scattered militias that constitute the Free Syrian Army, as well as whatever local civilian rule has emerged.

The border between Turkey and Syria is huge, across the entire northern slope of Syria. The possibility for further incidents is almost assured, as will be speculation from the Syrian government about Turkish support for the insurgency. Add into that the NATO directive and Turkey’s NATO membership, and you have a combustible mix.