The news from Australia, one of the coalition partners fighting ISIS in Syria, was described as a blow for the US, putting it in a "very difficult position" at a critical time as the battle to liberate the ISIS stronghold of Raqqa
"This is not the time for the coalition to be in disarray," Dr Lina Khatib, head of the Middle East and North Africa Programme at Chatham House, an international affairs think tank, told CNN.
In a statement issued Tuesday, the Australian Department of Defence said: "As a precautionary measure, Australian Defence Force strike operations into Syria have temporarily ceased.
"ADF force protection is regularly reviewed in response to a range of potential threats. ADF personnel are closely monitoring the air situation in Syria and a decision on the resumption of ADF air operations in Syria will be made in due course. ADF operations in Iraq will continue as part of the coalition."
Australia's decision came after a US Navy fighter jet shot down a Syrian warplane on Sunday. The US said it took the action to defend the US-backed Syrian Democratic Forces (SDF), a rebel group fighting ISIS on the outskirts of Raqqa in the northeast.
The incident -- the first of its kind since the US started fighting ISIS in Syria in 2014 -- prompted Russia to issue a threat to coalition aircraft flying west of the River Euphrates that they "will be considered air targets."
The Russian Ministry of Defense called the downing of the plane "a cynical violation of the sovereignty of the Syrian Arab Republic" and "military aggression."
As a result, it said, Russia has stopped using a key "de-confliction" communication channel set up to avoid conflict between US and Russian forces in Syria.
"Australia is worried about the suspension of the de-confliction line between Russia and the United States as a result of the downing of the Syrian jet," said Chatham House's Khatib.
"This could expose Australia to the risk of potentially clashing with Russian aircraft inadvertently.
"This is a risk that I am sure other countries participating in the international coalition share. Australia's protective measure of suspending its activities is likely to cause wider concern among the other participants in this campaign.
"The US position militarily is weaker and any sign of lack of unity within the international anti-ISIS coalition can only be good news for Russia and the Syrian regime."
The UK, another key coalition ally, said it would continue to take part in air operations despite Russia's warning.
"Air operations continue and de-confliction measures are ongoing," a UK government spokesperson said Tuesday. "We call on Russia to continue to use these measures."
Forces with competing aims are currently at close quarters in eastern Syria.
The United States is aggressively backing the SDF, a Syrian rebel alliance, as it fights its way into Raqqa
, supported by intense coalition airstrikes.
Meanwhile the Syrian army and its allies are also closing in on Raqqa and last week the Syrian military reached areas controlled by the SDF, making clashes between the opposing alliances almost inevitable.
Meanwhile Iran's military said Sunday that it has launched several medium range ballistic missiles
into eastern Syria, targeting ISIS fighters in retaliation for twin attacks that rocked Tehran on June 7.
The strikes are the first time Iran has fired missiles at another country in three decades and represent a major escalation of Iran's role in the war in Syria.
In a statement issued Tuesday, the Soufan Center, a security and intelligence firm monitoring the conflict, said: "The sheer number of rival military operations and escalating tensions in Syria makes miscalculations more likely than ever, with the potential for enormous consequences."
And two further incidents on Monday look set to heighten tensions between the US and Russia further.
A US fighter jet shot down a pro-regime drone
near al-Tanf in southeastern Syria, just outside the de-confliction zone according to the officials. The drone was assessed to be armed and in firing range of US troops.
And a Russian fighter jet flew within five feet of a US Air Force reconnaissance aircraft in the Baltic Sea, according to a US official.
The Russian plane was armed and flew "erratically", the official added, describing the encounter as "unsafe".