Washington: The United States demanded that the Syrian regime and its ally Russia end their "despicable" operation in Idlib province and vowed to support Ankara after 33 Turkish soldiers were killed.
"We stand by our NATO ally Turkey and continue to call for an immediate end to this despicable offensive by the Assad regime, Russia and Iranian-backed forces," a sState Department spokesperson said.
"We are looking at options on how we can best support Turkey in this crisis," he added.
The State Department said that US officials were seeking information from their counterparts in Turkey, where an official in a border province said that 29 soldiers were killed in the air strike in Idlib.
Reacting earlier to preliminary reports of the deaths, Kay Bailey Hutchison, the US ambassador to NATO, said the incident amounted to a "huge change".
Read: 33 Turkish soldiers killed in govt offensive as tensions mount in Syria
US relations with Turkey deteriorated sharply last year over Ankara's military intervention in Syria as well as its purchase of Russia's S-400 missile defence system in defiance of warnings from allies in NATO, an alliance created to counter Moscow.
"I hope that President Erdogan will see that we are the ally of their past and their future and they need to drop the S-400," Hutchison told reporters in Washington.
"They see what Russia is, they see what they're doing now, and if they are attacking Turkish troops, then that should outweigh everything else that is happening between Turkey and Russia," she said.
The US says the S-400 system will hurt NATO by allowing Russia to improve its tracking of Western aircraft.
Turkey insists it will set up the S-400 in areas not frequented by US jets and it has not yet put the system into operation, giving Washington hope that Ankara may still change its mind. (AFP)
