It depends if it's a triband phone. Actually a dual band phone would do! - in Europe, we have two GSM bands.

One is the standard 900 MHz "old" style GSM, used by Vodafone and mmo2 in the UK. The other is the PCS frequency, at 1,800 MHz, used by Orange and T-Mobile (and Virgin) and so on.

America uses the 1,900 MHz spectrum, so a true international phone has to use all three. If you have a 1900 plus 1800 phone, though, that would work.

I have no idea if there is such a beast...