Secretary of State John Kerry on fighting ISIS, Iran deal

Secretary of State John Kerry spoke with "CBS Evening News" anchor and managing editor Scott Pelley about the challenges of training Syrians to fight theIslamic State of Iraq and Syria (ISIS or ISIL) and sellingthe nuclear deal with Iran to Congress.

Kerry: U.S. counts on local allies to help fight ISIS

(on training Syrians to fight ISIS)

John Kerry: This is tough. And obviously it didn't go well. I think it's admirable that they've admitted it wasn't what they wanted it to be. There are, you know... The complexity of that battlefield cannot be overstated. So I think the numbers of different people, who's turning on who and it underscores the complicated fight against Da'ish, ISIL.

Scott Pelley: Is the war against ISIL worth fighting?

Kerry: Absolutely.

Pelley: Then why isn't it worth fighting decisively?

Kerry: I think that the question is, who's gonna make that decisive difference? The president has decided -- and, I think, appropriately -- that American forces are not the ones best suited to be able to take that fight at the moment, that it's not in the best interest of our country.

Secretary Kerry is campaigning for the nuclear deal he struck with the Iranian foreign minister. Iran agreed to dismantle most of its nuclear program in return for the lifting of crippling economic sanctions.

Kerry on U.S. prisoners in Iran: We didn't want to be "hostage to this agreement"

Kerry: We're not asking anybody to trust Iran. They're, they're -- Iran doesn't trust us. We don't yet trust them. And who knows what the future brings? So this agreement is built on real-time verification now. Iran, in order to get any sanctions relief, has to reduce its program very significantly. It has to destroy its core reactor and its, and its plutonium heavy water reactor. It has to take all of its enrichment out of other facilities. It has to hold its program back to 300 kilograms of stockpile of low-enriched material for 15 years. We are convinced through our intelligence community and through our energy department, which is responsible for nuclear weaponry, that we will know what Iran is doing.

Pelley: One of the key criticisms of the agreement is a provision that allows the possibility of up to 24 days before international inspectors would be allowed into an Iranian undeclared nuclear site. Let me show you what Prime Minister Benjamin Netanyahu told us about that.

"In fact, you have to give them not 24 hours notice inspecting a suspect site, but 24 days notice," Netanyahu said. "Now can you imagine, you're a drug dealer and somebody tells you, 'I want to inspect your premises?' That's a lot of time, 24 days, to flush a lot of meth down the toilet."

Scott Pelley asks John Kerry if China or Russia is reading his emails

Pelley: Your reaction?

Kerry: Well, my reaction is, with all due respect, nuclear material is not like drugs. You can't flush it down the toilet. You can't get rid of nuclear material that way. It lasts for hundreds, thousands of years.

Pelley: They [Iran] cannot build a nuclear weapon over the next ten years under this agreement?

Kerry: No. They cannot. Not possibly under this agreement.