In interviews with The Atlantic magazine published today, Obama also called out US allies who call for tougher US action in Mideast conflicts but fail to take risks themselves, describing them as "free-riders."
He cast the sectarian conflicts in the region as a competition between Iran and close U.S. Partner Saudi Arabia, and he urged both to find "an effective way to share the neighborhood."
Of his 2013 decision not to strike Assad's government, he said: "I'm very proud of this moment."
Obama had been close to ordering strikes to punish Assad for using chemical weapons against Syrians, with plans for military action ready to go. At the last minute, he said he'd ask for permission from Congress. The strikes never happened.
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Obama acknowledged the broad perception that "America's credibility was at stake" in the 2013 decision not to strike. Yet he said that "ultimately it was the right decision to make."
In the interviews, which took place over many months, Obama offered an unusually blunt assessment of American allies in Europe and in the Persian Gulf region, especially regarding Libya, where a 2011 NATO intervention backed by the U.S. Led to a vacuum of power that has fueled chaos and allowed extremist groups to thrive.
"What has been a habit over the last several decades in these circumstances is people pushing us to act but then showing an unwillingness to put any skin in the game," Obama said.