Jeffrey D. Sachs urges the US to end its "disastrous role" in Syria, because there are already far too many cooks in the tiny ktichen there - Iran, Israel, Qatar, Russia, Saudi Arabia and Turkey. The US, together with Qatar, Saudi Arabia and Turkey have been adamant about Assad's removal ever since the onset of the war in 2011. However appalling the regime is in Syria, Assad is not going anywhere. The author names "four main reasons for the failure" to topple Assad.

First, it is true that the Assad regime enjoys support not only from the Alawites (10% of the population) but "also Syrian Christians (10%) and other minorities (5%) "who feared a repressive Sunni Islamist regime." But as long as Assad remains in power, there is little hope that the Sunnis (75%) agree to a national reconciliation, since the socio-ethnic fabric has been torn beyond repair.

Second, unlike the autocrats in Egytp, Libya, Tunisia and Yemen, who had been deposed - the Libyan dictator, Muammar Gaddafi was lynched to death in his home town, Sirte - Assad remains in power, struggling to survive the 7-year long war - thanks to Iranian and Russian backing.

Third, when the Islamic State set up its stronghold in Raqqa, Syria, the US "diverted significant resources to defeating it, rather than to toppling Assad." But since ISIS were driven out of Iraq and Syria, the US is focusing on backing its allies - the Syrian Democratic forces, led by the Kurds - to prevent Assad from regaining control of the whole country.

Finally, the "anti-Assad forces have been deeply and chronically divided" and are backed by Qatar and Saudi Arabia - two oil-rich Sunni states that embrace different versions of Islam. This pits Doha against Riyadh, especially when Qatar has a good relationship with Iran.

Besides, Turkey is seeking to prevent the US-backed Kurdish fighters from holding onto territories on the Turkish border, fearing the embolenment of the Syrian Kurds would only inspire the Kurds in the east and southeast of Turkey to break away and fulfil their dream of a Greater Kurdistan,

The author has always said the US is fighting proxy war against Iran and Russia in Syria. What started as a "secret war" by Obama in 2013, when the CIA began to arm and train Syrian rebels, with Saudi Arabia providing substantial financing of the armaments, the US has been shifting its focus several times. As the situation on the ground in Syria is fluid, the war is also getting murkier.

Iran and Russia are remaining in Syria - an occupation approved by Assad - because his army suffers from exhaustion and would have been defeated without the backing of Iran and Russia.

Iran is keen on having Syria as a land corridor from Tehran to Beirut, where the Iranian-backed militia group, Hezbollah is a powerful force in Lebanon.

With an airbase and a naval base in Syria, Putin has finally cemented his influence in the Middle East.

Israel's role in the fray aims at launching raids against Iranian targets in Syria, seeking to decimate Tehran's support of the Hezbollah, which had fought Israel in the 1980s.

The problem is that the multi-layered conflicts and a panoply of actors fighting in Syria makes it resistant to international mediation. The war has a different dynamic with largely static front lines. The West has largely given up on Assad's removal, tacitly accepting his continued rule and leaving Russia, Iran and Turkey to dominate the region.

International tensions threaten unpredictable new escalations with the US involvement - a mission creep - and Turkey’s recent incursion on the Syrian border to fight the US-backed Kurds. The possibilities of clashes between the US and Turkey - two NATO allies - as well as the US and Russia have also increased. It remains to be seen how long Iran, Russia and Turkey can afford to fight a war of attrition. The Kurds, and the anti-Assad forces may fight to the bitter end, even though Assad is eager to end the war and focus on rebuilding the country.

Some European and Asian countries are said to be jockeying for contracts in the multibillion-dollar reconstruction, and Russia and Iran have already won infrastructure concessions. The question is how much longer and deadlier the war will be, before it ends - even without the US.