Washington has reportedly reprimanded its Syrian Democratic Forces (SDF) allies in northeast Syria for holding up banners depicting the leader of the Kurdistan Workers Party (PKK), Abdullah Ocalan, during rallies in the SDF-controlled area.

The top U.S. military commander overseeing the Middle East said Tuesday that despite the nuclear deal, Iran shows no signs of altering its destabilizing behavior.

"There are a number of things that lead me to personally believe that, you know, their behavior is not — they haven't changed any course yet," said Army Gen. Lloyd Austin, commander of U.S. Central Command, at a Senate hearing.

Washington continues its support for Assad's PYD allies with the construction of two military airbases in Syrian Kurdistan (commonly referred to as Rojava)

Following the recent severing of relations between Iran and Saudi Arabia over the execution of Shiite cleric Sheikh al-Nimr by Riyadh and the torching of the Saudi embassy in Tehran, some in the Iraqi government fear it will exacerbate Sunni-Shiite tensions at a critical juncture.

This comes as Sunnis and Shiites in Iraq have spearheaded fragile cooperative efforts to tackle the threat posed by the Islamic State (ISIS). Now the fear is that such cooperation could be compromised as a result of the recent tensions and war of words between Riyadh and Tehran.

Casting aside U.S. concerns about aiding extremist groups, Turkey and Saudi Arabia have converged on an aggressive new strategy to bring down Syrian President Bashar Assad.

The two countries — one a democracy, the other a conservative kingdom — have for years been at odds over how to deal with Assad, their common enemy. But mutual frustration with what they consider American indecision has brought the two together in a strategic alliance that is driving recent rebel gains in northern Syria, and has helped strengthen a new coalition of anti-Assad insurgents, Turkish officials say.