bill weir, thank you so much. >>> and now to the former mexican foreign minister jorge castaneda. he says if the people marching want to claim asylum in the united states they should be allowed to cross through mexico. he's joining me now, in fact, from new york. mr. castaneda, that is pretty provocative. you're basically saying, hey, you want to go to the united states, go through mexico and you should be able to get to your destination. >> absolutely, christiane. good to be with you. it's very important to understand that the united states has been pressuring mexico for several months now for mexico to agree to what president trump said. that is that asylum should be requested in mexico. but mexico has not agreed to that, and it shouldn't agree to that. some people want to request asylum in mexico, about 1,000 have. those requests will be processed. some will be granted. others not. but other people don't want to stop in mexico. they want to go to the united states. mexico should not be doing the united states' dirty work for it. these people should be allowed to reach the border

we get the latest on the ground, and we speak to the former mexican foreign minister jorge castaneda. >>> then, is america losing its longest war?i speak to stanley mcchrystal, former commander of allied troops in afghanistan. >>> and our walter isaacson obes the origins of life, the universe and everything with theoretical physicist, brian green.