WASHINGTON — The United States scrambled today to calm escalating tensions in Syria a day after the US-led coalition shot down an Assad regime warplane and Iran launched missile strikes against the Islamic State (IS).

Sunday's destruction of a Soviet-era fighter-bomber by a US Navy jet marked the first time that the United States has shot down a Syrian aircraft in the six-year civil war. That same day, Iran fired several missiles at IS targets in Deir ez-Zor, eastern Syria, the first time in more than 15 years that Tehran has fired missiles at a foreign country.

Further escalation between rival forces “doesn’t help anybody,” White House press secretary Sean Spicer told journalists today. "While we want to de-escalate the situation there … we will always preserve the right to self-defense.”

New flashpoints have emerged as US-backed Syrian opposition forces have intensified the push to retake the IS stronghold of Raqqa. Pro-Syrian regime forces, backed by Iran and Russia, have clashed with US-backed Syrian opposition forces in eastern Syria in recent weeks.