US President-elect Donald Trump on Friday (16 December) reiterated his promise to build "safe zones" in war-torn Syria to present them as a way to stem the tide of civilians into Europe. But President Barack Obama said the idea would be a tough challenge to enforce because of Russia and Iran.

"We're going to try and patch that up and we're going to try and help people," Trump told his supporters during a rally in Florida. "We're going to build safe zones. We're going to get the Gulf States to pay for the safe zones."

Trump made a similar statement during his rally in Pennsylvania on Thursday (15 December).

However, the idea is too good to put into practice as it presents a "continued challenge", Obama said. The safe zones would require maintenance by ground forces unless Trump can win the cooperation of President Bashar al-Assad's regime and its allies – Russia and Iran.

Both the American leaders spoke at different occasion about the conflict and their comments come amid efforts to evacuate thousands of civilians from Aleppo. The evacuations of rebel fighters, their families and the injured from east Aleppo were suspended on Friday after several weeks of bombardments by the Syrian army.

Obama hoped Damascus and Moscow would let the remaining civilians in Aleppo to leave the city safely by responding to the international pressure over the handling of the crisis there.

The president also defended Pentagon's approach toward Syria and said he understood the urgent call to end the civil war, which has been plaguing the Middle Eastern country for close to six years now.

"I cannot claim that we've been successful. And so that's something that, as is true with a lot of issues and problems around the world, I have to go to bed with every night," Reuters cited Obama as saying, on Friday (16 December).

"Unless we were all in and willing to take over Syria, we were going to have problems," he continued. He ran office on a promise to reduce the number of US troops stationed in war zones.

"Everything else was tempting because we wanted to do something and it sounded like the right thing to do, but it was going to be impossible to do this on the cheap," he said, while defending Pentagon's decision on Syria but blamed Assad for the bloodshed.

Donald Trump US president-elect
US President-elect Donald Trump said he would get the Gulf countries to pay for a safe zone that he wants to build in Syria to help civilians flee to Europe Getty Images