"These are very troubled times in the Middle East. And we see what happened just recently, yesterday in Syria. Horrible. Horrible thing. Unspeakable," Trump told reporters as he hosted Jordan's King Abdullah in the Oval Office.
Trump said the two leaders were going to have some interesting discussions.
He described the use of chemical weapons against people as a terrible affront to humanity.
"Terrible. Terrible. It is a terrible affront to humanity. I can tell you. Terrible," he said.
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Meanwhile, Senator John McCain, Chairman of the Senate Armed Services Committee, said that after six years of indecision and inaction, Trump has been left with no easy options in Syria.
"Yet as difficult and complex as our challenges are, President Trump and his administration have an opportunity to finally change course and take action to address this strategic and humanitarian disaster, which has led to more than 400,000 Syrians killed and six million displaced," McCain said.
"Seizing this opportunity will require answering some very difficult strategic questions. But until we do, the war, the terror, and the refugees will continue, and America's national security interests will be placed at greater risk," he said.
"As we once again bear witness to innocent people writhing on the ground and gasping for breath, we know Assad not only disregarded his chemical weapons commitments, but continues to carry on mass atrocities with impunity. Unless and until Assad pays a price for his brutality, the slaughter and destruction in Syria will go on," he said.