And in case you didn't read that link I posted, here's Trump directly telling Nieto Mexico has to pay for the Wall.

The only thing I will ask you though is on the wall, you and I both have a political problem. My people stand up and say, “Mexico will pay for the wall” and your people probably say something in a similar but slightly different language. But the fact is we are both in a little bit of a political bind because I have to have Mexico pay for the wall – I have to. I have been talking about it for a two year period, and the reason I say they are going to pay for the wall is because Mexico has made a fortune out of the stupidity of U.S. trade representatives. They are beating us at trade and they are beating us at the border, and they are killing us with drugs. Now I know you are not involved with that, but regardless of who is making all the money, billions and billions and billions – some people say more – is being made on drug trafficking that is coming through Mexico. Some people say that the business of drug trafficking is bigger than the business of taking our factory jobs. So what I would like to recommend is – if we are going to have continued dialogue – we will work out the wall. They are going to say, “who is going to pay for the wall, Mr. President?” to both of us, and we should both say, “we will work it out.” It will work out in the formula somehow. As opposed to you saying, “we will not pay” and me saying, “we will not pay.”

Because you and I are both at a point now where we are both saying we are not to pay for the wall. From a political standpoint, that is what we will say. We cannot say that anymore because if you are going to say that Mexico is not going to pay for the wall, then I do not want to meet with you guys anymore because I cannot live with that.