We’ve selected the five biggest takeaways from the conversation.

#1 The Russian Proposal Could Work  — If They Cut a Deal Fast  

Kerry said that a Russian-brokered deal to hand over Syria’s chemical weapons could stop a U.S. strike on Syria. “If we can in fact secure all of the chemical weapons in Syria through this method, clearly, that’s by far the most preferable and would be a very significant achievement,” he said. “It is clearly preferable to use of force, which, in the end, wouldn’t in fact contain all of the weapons.”

But the details of a complex deal would have to be sorted out, in short order. “We’ve made it very clear in our conversations with the Russians this has to be done quickly,” Kerry said. He didn’t commit to a time frame for how long the U.S. will wait – how much of a diplomatic runway would be tried before resorting to a military action. He said that choice is at Obama’s discretion.

Kerry heads to Geneva for talks with his Russian counterpart on Thursday. In our interview, he sounded somewhat optimistic they would bear fruit.

“I hope – and I think so far, there are indications we will at least be able to have a serious conversation,” he said.

If diplomacy fails, the U.S. would face a tough choice on how to move forward with a Syria strike, given the current levels of political support.

“Common sense tells us we don’t want to buy into something that isn’t going to get the job done, then we’re right back where we started from. So this has to be a transparent, accountable, fully implementable, and clearly verifiable process, and we’re going to have to work at how that’s going to be achieved.”

#2 Assad Still Has Control of His Weapons, So He Can Turn Them Over 

Kerry downplayed concerns around the difficulty of collecting or controlling Syria’s chemical weapons stockpile — he said the Assad regime is in a good position to hand them over.

“For better or worse, the fact that Assad has been running a highly controlled and very hierarchical process has forced them to contain all of these weapons in the regime-controlled areas. As a result of that, it is our argument that they therefore can control access to these sites,” he said.

“We believe that they need to show us an entirely verifiable, completely accountable, and ongoing verifiable process by which we know we have all of the weapons, access to any sites in question, unlimited access, investigation, verifiability.”

#3 This Plan Was in the Works, Even Before the “Gaffe”  

Even before Kerry’s apparent slip at a London press conference, Russia and the U.S. were talking about a possible deal.

“We’ve had conversations about chemical weapons for some period of time, and we have talked about the issue of trying to gain control of them both at the United Nations as well as in bilateral conversations with the Russians. But most specifically, we discussed this last week,” he said.

“Sergey Lavrov, the Foreign Minister of Russia, and I discussed it. President Putin discussed it with President Obama in St. Petersburg. And President Obama instructed him that both – that we would take it up at the foreign minister level and see if it, in fact, had any life in it, if it could be real. I obviously mentioned it in public in London on Monday, and we are where we are today.”

#4 The U.S. Bottom Line is a Full Security Council Resolution

In response to a question from Kristof, Kerry said the U.S. needs a full Chapter 7 Security Council resolution to make the Russian deal work. That would allow for the U.N. to hold Assad accountable, issue sanctions or military action in punishment if the offer to hand over chemical weapons falls through.

“We need a full resolution from the Security Council in order to have the confidence that this has the force that it ought to have,” he said. “It also has to have consequences if games are played or if somebody tries to undermine this, and I think the whole world needs to invest in that. I believe the world is ready to invest in that.”

But Russia disagrees. It has rejected the notion, asking the U.S. to take the threat of a military strike off the table. Russia has veto power at the Security Council and could block a Chapter 7 Resolution from going through.

“The Russians are in a slightly different place on that,” Kerry said. “We’ll have to see where we get to.”

#5 In Any Event, the U.S. Will Send More Aid to the “Moderate Rebels” 

Kerry said that President Obama has decided to increase support to the “moderate opposition,” which he identified as rebel groups 30,000-40,000 strong, under the command of General Salim Idriss. Those forces, part of what’s known as the Free Syrian Army, have often complained that they U.S. and its allies have failed to back them, by not to send decisive levels of weapons and material support.

“It is accurate to say that some things have not been getting to the opposition as rapidly as one would have hoped,” said Kerry. When pressed, Kerry wouldn’t say specifically what kind of things those would be.

“It is ramping up, but I can tell you that many of the items that people have complained were not getting to them are now getting to them,” he said. “A coordinated effort is being made among the many supporters of the moderate opposition to get them the assistance they need.”

Kerry suggested there is a “firm barrier” between aid to the Free Syrian Army and Al Qaeda-linked groups like Jabhat al Nusra — though sources on the ground have told Syria Deeply that moderate and extremist brigades sometimes work together.

Commenting on their out-sized influence, Kerry conceded that Al-Qaeda linked groups in Syria “have proven themselves to be probably the best fighters… they are the most trained and aggressive on the ground.”