Selling in UK, buying in US. 1031 an option?

[Alex Miles]

Hi, need some advice!

Next spring I will be putting my flat in London on the market. I bought it in 2010 with a mortgage (a private loan from a friend) the price has almost doubled by now, and as I got married to an American in 2011 - I have been here in Atlanta most of the time since then. The flat has been rented out for the past year and a half.

I would like to sell it and buy rental property here. 

I have an ITIN, but no Social Security number as Immigration just delay and delay. I can't put my life on hold any longer, and I always file jointly for taxes with my partner, if that helps.

I heard about the 10% witholding, and that it can be avoided if necessary, but I don't know how I'd go about rolling the sale of a UK property to another person in the UK when I think, for a 1031, it has to go via an intermediary who, I'm guessing, is in the US.