WASHINGTON • According to the Pentagon, the United States still has no intention of getting involved in Syria's six-year civil war; the American presence there is solely to help its allies defeat the Islamic State in Iraq and Syria (ISIS).

But a recent spate of incidents has sparked alarm from diplomats and national security officials that the US may be inadvertently sliding into a far bigger role in the Syrian civil war than it intended.

"We don't seek conflict with anyone other than ISIS," Captain Jeff Davis, a Pentagon spokesman, said on Wednesday.

But this month alone, the US shot down a Syrian warplane, came close to shooting another and downed two Iranian-made drones that were nearing US-backed troops on the ground.

Russia has retaliated by threatening to treat American planes as targets; in a dramatic Top Gun-style manoeuvre on Monday, one of Moscow's jets buzzed within 2m of a US spy plane. Russia has also suspended its communication channel with the US on military operations in Syria.

With each episode, "we own more of the conflict in Syria without articulating a strategy", said Professor Vali Nasr, dean of the Johns Hopkins School of Advanced International Studies.

"We are sleepwalking into a much broader military mandate, without saying what we plan to do afterward."

ISIS is now reeling in Syria. It has been battered by strikes from a host of enemies - from the US and its regional allies to the Syrian government that is backed by Russia and Iran. It no longer holds one-third of the country, according to US officials who say that the group has lost around half of the territory it once controlled.

Now, all sides are converging on a smaller piece of territory, resulting in competing forces increasingly turning on one another, in addition to the common enemy.

The Pentagon's Captain Davis noted that when US-backed ground troops are confronted by "armed drones, that leaves us with no choice but to defend ourselves and our partners". He said that the downing of an Iranian-made drone this week was done in self-defence. Defence officials insist that does not amount to a greater US involvement in the broader war.

But privately, US military officials acknowledge that they are quickly running out of space in Syria to stay out of President Bashar al-Assad's way - not to mention Russia and Iran.

In Europe, France President Emmanuel Macron has announced he would be taking a distinctly different tack on Syria than his predecessor, saying that getting rid of Mr Assad is no longer a top priority. Instead, he said, getting rid of terrorists is more important - and he is prepared to work with anyone towards that end, including Moscow.

But at the moment, there are no ongoing talks among the major parties over what to do once ISIS is defeated in Syria.

Meanwhile, Moscow yesterday said two Russian warships and a submarine in the Mediterranean have fired missiles at ISIS targets in Syria. The Russian Defence Ministry said Turkish and Israeli military "were informed in a timely manner of the missile launches through communication channels", but it did not mention the US.

NYTIMES, AGENCE FRANCE-PRESSE