The Syrian government set conditions on Thursday for any international inquiry into a suspected chemical attack that killed scores of people, saying it must not be "politicized" and should set out from Damascus and not Turkey.

Foreign Minister Walid al-Moualem said Syria's past experience with international inquiries had not been encouraging. The government would only decide on the idea once its concerns were addressed, he said.

Moualem also reiterated the government's strong denial that it was behind the attack on Tuesday in Khan Sheikhoun in the northwestern province of Idlib, an area mostly controlled by rebel groups at the border with Turkey.

U.S. President Donald Trump on Wednesday said President Bashar al-Assad's government had gone "beyond a red line" and said his attitude toward Syria and Assad had changed. But he gave no indication of how he would respond.