President Barack Obama struggled to defend his administration’s policy on Syria in a contentious and somewhat combative interview with CBS’s “60 Minutes” Sunday program.

“What I have also said is, is that surprisingly enough it turns out that in a situation that is as volatile and with as many players as there are inside of Syria, there aren’t any silver bullets,” Obama said while measuring his words in a slow-moving manner. “And this is precisely why I’ve been very clear that America’s priorities has to be number one, keeping the American people safe. Number two, we are prepared to work both diplomatically and where we can to support moderate opposition that can help convince the Russians and Iranians to put pressure on Assad for a transition. But that what we are not going to do is to try to reinsert ourselves in a military campaign inside of Syria.”

“The solution that we’re going to have inside of Syria is ultimately going to depend not on the United States putting in a bunch of troops there, resolving the underlying crisis is going to be something that requires ultimately the key players there to recognize that there has to be a transition to new government. And, in the absence of that, it’s not going to work,” he added.

When pressed over Russia “challenging” Obama’s leadership by propping up Assad in Syria, the president turned defensive by arguing that the U.S. is still head of a worldwide coalition against Assad.

“Mr. Putin now is devoting his own troops, his own military, just to barely hold together by a thread his sole ally,” Obama asserted. “We’ve got a 60-country coalition that isn’t suddenly lining up around Russia’s strategy. To the contrary, they are arguing that, in fact, that strategy will not work.”

“He’s challenging your leadership, Mr. President. He’s challenging your leadership,” host Steve Kroft pushed back.

“My definition of leadership would be leading on climate change, an international accord that potentially we’ll get in Paris,” Obama responded. “My definition of leadership is mobilizing the entire world community to make sure that Iran doesn’t get a nuclear weapon.”

After pushing back against critics of America’s allies in the region, as well as of some back at home, the president was asked if he thinks the world’s a safer place, as he draws closer to the end of his second term? To which Obama replied: “America is a safer place. I think that there are places, obviously, like Syria that are not safer than when I came into office. But, in terms of us protecting ourselves against terrorism, in terms of us making sure that we are strengthening our alliances, in terms of our reputation around the world, absolutely we’re stronger.”

The administration’s policy on Syria has been challenged by some in the Democratic Party, including, most recently, Democratic presidential frontrunner Hillary Clinton and Senator Tim Kaine.

Read the entire transcript of President Obama’s interview here