Following United States President Donald Trump's abrupt tweet on Dec 20 announcing the pullout of US troops from Syria, there was no lack of suspicion and criticism.

James Mattis, then defense secretary who resigned after Trump declared that all-important decision on Twitter, was only one of many who had difficulty endorsing it.

Many questions have been raised. Not least about the way a decision of far-reaching strategic significance was made. While bringing US servicemen and women home from the dangerous war zones of Syria does honor another of the US president's campaign promises, giving him one more chance to repeat the claim "promise kept", doing it in such a rash manner may create more problems than it solves.

For one thing, despite Trump's claim of "historic victories" against the Islamic State extremists in Syria, many at the Pentagon reportedly disagree with the conclusion that the IS terrorist organization has been defeated.

And what has happened in war-torn Syria over the past two weeks following Trump's announcement? Accumulating signs of fresh violent rivalries among different regional actors with conflicting agendas.

Still, withdrawal was the order, and Trump is the US commander-in-chief.

The withdrawal was initially anticipated to be completed within weeks, but it seems that the US leader has finally woken up to the complexity of the matter and has now changed his tune.

While sending White House National Security Advisor John Bolton to the Middle East to assure confused allies and partners, Trump clarified Sunday: "I never said we're doing it that quickly."

According to Bolton, US troops will not leave until the IS militants are defeated, and American-allied Kurdish forces get proper protection. The timetable is based on objectives that "we want to accomplish", Bolton told reporters in Jerusalem.

If, as he said, the pullout will not occur until the IS group "is defeated and is not able to revive itself and become a threat again", and security of Israel and other US "friends" in the region "is absolutely assured", there will be a protracted process ahead. Not to mention US geopolitical concerns regarding Russia and Iran simply will not allow the US to be a disinterested onlooker there.

A rethink on the withdrawal was therefore called for, because ensuring the IS militants are vanquished is necessary for the US to accomplish its other objectives.

Now it is to be hoped the US will be good to its word and not withdraw until the IS group is defeated and unable to revive itself, as eliminating the terrorist group is also the precondition for reconstruction and stability in Syria.