Nokia Lumia 920 AT&T Frequency Help

[MessiaaH]

I currently own an HTC Titan (UK Model), and I desperately want a Lumia 920

Question:

Does anybody know if LTE is backward compatible with HSPA+ ?
My Carrier supports 2100 MHz HSPA+, if i use a 3G, or HSPA device, it will work at those speeds on the network.
I'm trying to figure out if an LTE 2100MHz device (Lumia 920), will work at HSPA+ speeds on my carrier.
(Lumia 920 AT&T is cheaper than UK International model, so i'd get that if it works with H+ network.)

Thanks!