In an interview with MSNBC's Andrea Mitchell, outgoing Secretary of State John Kerry, discusses the Obama administration's efforts over the past few years to defeat Syrian President Bashar al-Assad by arming and supplying rebels in that country.



He retells the war in Syria, as he saw it play out.



He said: "Together, Iran and Russia had to prop [Assad] up, and save him from the possibility that the extremists might take over the country."





ANDREA MITCHELL: Five years. So many people dead. Displaced millions. The suffering. Russia, the game-changer, a year and some months ago entering with no warning, 24 hours after meeting personally with President Obama, Putin's planes are flying over Syria for the first time. No warning at all to us. The Russian role has been so devastating in propping up Assad at a critical juncture.



Any regrets? You expressed some that were in an overheard audio to some of the opposition leaders. Any regrets that we didn't arm the rebels sooner, when there might have been a better opportunity?



JOHN KERRY: Well again, Andrea, I'm going to have a lot of opportunities to be able to look back and digest what choices might have been made. I'm not going to do it now... Except to say to you, very clearly, that I'm proud of all the efforts we made to try to lead people to a peaceful resolution. And in fact, the only solution to Syria will be a peaceful agreement along the lines of what we laid out... and the several communiques that we issued, and the United Nations resolution that we passed. 2254. Those will be the basis for whatever happens, if they get there.



I believe there is an exhaustion setting in, sometimes timing is everything in these kinds of negotiations. And I believe that there is a possibility over the course of the next year that the parties could come forward. It would be on a different plane of leverage, a different kind of outcome than some people might have anticipated. But there may be possibilities of trying to move forward...



There is no military solution to the problem of Syria. When President Putin came in, he came in partly to prop up Assad, but also because ISIL/Da'esh was gaining huge ground. The radical extremists were gaining huge ground against Assad, and Assad was in a very fragile position. And so together, Iran and Russia had to prop him up, and save him from the possibilities that the extremists might take over the country.



And I will say, that was not something that we weren't also concerned about -- that there was a gaining foothold of al-Nusra, and Da'esh, in their ability to push towards Damascus. And the regime was on its heels. Did Putin make an enormous difference in that? Yes, along with Iran and Hezbollah and the entities that basically overwhelmed some of the forces available to the opposition. But that doesn't end the war. Nothing that he has done is in fact going to obviate the need to get to Geneva to have... a real negotiation that resolves the political differences [in Syria]...



That's a hard road to get to, no matter what Putin has done.

Watch Mitchell's full interview with Kerry below: