WASHINGTON

A pair of U.S. ambassadors on Wednesday maintained Turkey's right to defend itself by downing a Russian jet that violated its airspace. 

"I don't pretend to be an international lawyer, but Turkey's case seems crystal clear to me," Francis Ricciardone told Anadolu Agency. "It published its rules of engagement as it warned several years ago against intrusion from Syria on its national airspace," said the former ambassador to Turkey who served from 2011 to 2014.

He said Turkish authorities repeatedly warned against intruding pilots following the establishment of new rules of engagement in 2012 after a Syrian missile downed a Turkish jet. 

But after Russian aircraft twice last month violated Turkish airspace, Turkey publicly announced the rules of engagement.

In the face of 10 warnings in 5 minutes by Turkish Air Force fighters on patrol along the Syrian border, an unidentified aircraft crossed into Turkish airspace Tuesday and was promptly shot down by F-16s in line with Turkey's rules of engagement. 

"As far as I know, no government has challenged Turkey's assertion of its right to defend its airspace against foreign intrusions," said Ricciardone.

"It seems to me that Turkey has acted within its rights and responsibly in these matters."  

The veteran diplomat who also held the deputy ambassador post at the U.S. Embassy in Kabul, Afghanistan, also urged de-escalation between Russia and Turkey.  

"This is not a time for anger between these two major regional powers, but for cool, direct, responsible, and effective communications between them," he said. "It seems to me that Russia should share with Turkey extremely important national interests in managing this incident peacefully."

He noted the importance of bilateral interests between the two countries as well as with the US, Europe, and Arab world in terms of "regional peace and security".

International law recognizes a nation's right to protect its airspace against foreign incursions, according to former ambassador to Ukraine John Herbst. He told Anadolu Agency that Turkey's version of events is corroborated by NATO. 

"Turkey sent numerous warnings before shooting. That suggests that Turkey was fully in its rights in this incident," said Herbst.  

Noting Russian claims that its plane did not violate Turkish airspace, Herbst added: "To ‘prove’ this, the Ministry [of Defense of Russia] provided maps and radar date. Unfortunately for Moscow, bellingcat - social media experts in Great Britain, report that the radar data and map are mutually inconsistent. So Moscow’s evidence proves nothing."

He suggested that Turkey should call for a UN inquiry into the incident.

Herbst, whose tenure in Ukrain lasted from 2003 to 2006, also served in the same position in Uzbekistan. He warned Russia against military action in response to the incident, noting that it would be dangerous if Moscow takes a military posture against a NATO member. 

Russia might, however, take economic measures against Turkey such as banning commercial flight to the country, he said. 

"Russian policy in Syria has been strongly anti-western. It has spent most of its time bombing the weak opponents of the [Bashar al] Assad regime supported by Turkey and other western powers, instead of ISIL," he added. 

While conducting air operations against opposition, Russian jets regularly intruded the airspace of a NATO ally and those were actually "not accidents," he said.