Presidential spokesman İbrahim Kalın has said the struggle between the U.S. and Russia in Syria "must go beyond proxy wars and geopolitical muscling".
Writing for the Istanbul-based Daily Sabah, Kalın said: "It must focus on establishing a legitimate, democratic and inclusive political order without the Assad regime or terrorist networks like Daesh, al-Qaeda, PYD or YPG."
He said "there is strong evidence that the Assad regime used chemical weapons again on April 7".
He added the World Health Organization reported that about 500 people in Douma had been treated for "signs and symptoms consistent with exposure to toxic chemicals".
He reiterated the use of chemical weapons is just one part of the Syrian tragedy.
"The chemical attack on April 7 must be taken seriously and the regime must be held accountable for its war crimes.
"As President Recep Tayyip Erdoğan has rightly said, far more people have died as a result of the use of conventional weapons and the international community has failed to respond to this drama, leaving the people of Syria to the barbarism of the Assad regime on the one hand, and Daesh and other terrorist groups on the other.
"This is not the first time the regime has used chemical weapons. When it did so back in 2013, the U.S. President Barack Obama had set a red line but did nothing to prevent repetition of 'such barbaric acts'. This Obama's failure led Russia and Iran to enter into Syria and offered a lifeline to the Assad regime."
Kalın added: "Over the past four years, the Syrian saga has been used by world powers and regional players for their own geopolitical positioning. This is unlikely to change now.
"The main problem is that the focus is not ending the war but using it in various ways to exert influence in Syria, Iraq and beyond.
"It is the Assad regime and its backers that benefit the most from this geopolitical brinkmanship, and the Syrian people continue to suffer."
