We'll come back for more roundtable later. But we're going to turn now to national security. The world's biggest power, america's longest war and that emerging nuclear deal with iran all front and... See More
We'll come back for more roundtable later. But we're going to turn now to national security. The world's biggest power, america's longest war and that emerging nuclear deal with iran all front and center. We have an exclusive interview with president's former national security adviser tom donilon coming up. But first, here's some background from abc's muhammad lila. Reporter: One week changes it all. Last sunday, news of a historic deal, returning home triumphant. This is a win for iranians and for the other countries. Reporter: In the streets of tehran, we found signs of hope everywhere, from skateboarders who want americans to visit. I hope the relation gets better. Reporter: To teenagers hanging out at a fried chicken joint. But this week, it's back to reality, saudi arabia, america's longtime ally, is nervous about new deal and israel is sending teams to washington to lobby against it. All of this forcing secretary kerry to try reassure congress and allies overseas that the deal is narrow. And in neighboring afghanistan, another foreign policy headache, the standoff between president karzai and president obama continues, despite a diplomatic full-court press. After 12 years and more than 2,000 american troops killed, karzai is refusing to sign a long-term security deal with the united states. A drone strike this week that reportedly killed a young afghan boy only making tensions worse, if the deal isn't signed, america says it will pull all of its troops out next year. Meanwhile off the coast of japan, it's a symbolic fight. Take a look at this map. What china calls its new air can defense zone. They need permission. Even though the area covers two islands japan claims it owns. It prompted this warning from new ambassador to japan, caroline kennedy. Unilateral actions undermine security. Constitute an attempt to change the status quo in the china sea. Reporter: George, when two b-52 bombers entered the air space this week, they scrambled their own fighter jets to intercept it. George? Thank you very much. Let's bring in tom donilon. Here for his first sunday interview. Welcome to "this week," tom. Let's begin with that cat and mouse game going on in china. People look at that and say, why should we care about a couple of inhabitated islands. You have mjor powers there, china, korea and japan. China have unilaterally undertaken steps that have increased tensions. Most importantly, george, they present the prospect of the possibility of miscalculation in the states. Remember, in 2001, we had an incident, you had a fighter pilot killed with a u.S. Plane that had to land in china. That miscalculation and mistake that we have to be very careful going forward. When you were the president's national security adviser, you put a lot of energy and time, your personal time, in this so-called pivot to asia, should americans get used to the idea now that china is really our number one rival in the world? I'd look at this way, if asia is a principle opportunity for the united states and the world going forward, our prospects and asia's prospects are linked. It's a tremendous opportunity there. And secondly, for 60 years, the united states has provided the security platform on which asia's socioeconomic has been built. It's a critical role for the united states. Indeed our decision at the outset of the obama administration that we should put more effort into this. And provide additional effort and security in the region. Do a thought experiment. In this instance, if the united states were not presence, in terms of consulting and coordinating with our allies. Having vice president biden talking to chinese. Leaving today. Leaving today. You could see tensions rising to a really dangerous level. This has been a longtime role for the united states. It seems like the more the president and you try to make this pivot to asia, you're always getting drawn back into the commitments we already have, including afghanistan, back in the news. This week, we saw your successor, susan rice, go over to afghanistan, meet with president karzai, trying to get this long-term security pact signed, now he says he's not going to do it, raising new demands on the united states. The instinctive reaction is fine, if we doesn't want to sign the pact, we'll bring home our troops. President karzai should go ahead and sign the agreement. As we sit here this morning, the united states has 51,000 troops in afghanistan. 51,000 troops. But casualties way down. Casualties way down. We're in the process of withdrawing from afghanistan right now. We hope to accomplish that mission by the end of december 2014. Whether there should be support of presence of u.S. Troops after 2014 inside afghanistan. Why should there be? Well, for a couple of reasons. First of all, president karzai should sign the agreement. It's been approved by a large assembly of leaders. They got together and looked at the proposed agreement with the united states after 2014, and asked -- recommend that president karzai sign it. He should sign it. It's in our interest. That said, his refusal to sign it up to this point is reckless. I also adversely impacts our ability to plan for post 2014. Fine, if he doesn't sign it, we'll really pull everyone out? At some point, george, it becomes impossible to make those kind of plans. Number one. Number two, yes, if the united states doesn't have a bilateral security arrangement with afghanistan, that supports its troop presence there, the united states cannot be present in AFGHANISTAN AFTER DECEMBER 31st, 2014. And this has cascading effects. If the united states isn't there, then nato allies won't be there. Because they rely on the capabilities the united states provides. We won't have the same kind of support for the afghan national security forces. It's a very big point decision here for the afghans and president karzai. He should go ahead and sign the agreement. If he doubt, america will move towards plans -- by the way, america has a lot of options. Could that cost all of the gains that have been made in this long war? We think, at the end of the day, it will be better to have a continued presence in afghanistan. Again, as I said earlier to you, george, the united states has a lot of options in terms of protecting its allies in the region. Let's talk about iran. Some of president's allies in congress have been quite critical of the deal, it just freezes the iran program, it doesn't cause any rollback. You saw president rouhani of iran, saying iran is absolutely determined to maintain uranium enrichment sites. 100% red line for his government. If they maintain that position, can there be a permanent deal that works with iran? No, it's going to be rolled back of the uranium program for there to be a comprehensive deal at the end of the six months of negotiations. The interim steps are quite significant, and I think positive in this way, they freeze the program in place. They roll back portions of the program, especially the 20% enriched uranium. It provides intensive monitoring and it addresses something that israelis and we have been concerned about. The nuclear reactor. It's a very good foundation, a backdrop to have comprehensive negotiations. Very solid achievement by secretary kerry and president obama and the administration. The other thing that it does, george, is this, the israelis and we were concerned -- when you open up negotiations with iranians, they would use those negotiations to advance their program, that's not going to be the case here because everything is frozen in place during this time. We have seen that it's created a lot of upset -- not only in israel but also other allies in the middle east, saudi arabia, and it feeds into a general perception, like vladimir putin, like the saudis, that the president has been vacillating and week. How do you respond to that? I don't know how in this case you call the president vacillating and weak. We got here through a u.S.-Led, very tough isolation and pressure campaign. The centerpiece of that campaign was sanctions. The sanctions, the toughest put on any country. You wouldn't forced the choice. You wouldn't have had the election of rouhani. The direct line between sanctions, rouhani elected, because we put tremendous pressure on the iranian economy. We isolated iran. So, this is a u.S.-Led pressure to bring iran to the table. The test now is, whether the iranians can do they need to do. Finally, one final question about north korea. We have seen these questions this weekend of merrill newman, 85-year-old korean war veteran detained by the north koreans, they're basically charging him with war crimes, is there any way to deal with this country? What the country should do is release mr. Newman as of right now. They have had this political theater and they should release him in the interest of humanitarian gesture, his health and the right thing to do. This is an exceedingly difficult regime to do with. Tom donilon, thanks very much. When we come back -- the roundtable reacts from two surprise announcements.
This transcript has been automatically generated and may not be 100% accurate.