Virtex-II Pro and DDR2 SDRAM differential IO

I'm doing a Virtex-II Pro design that uses DDR SDRAM SODIMM modules as
data storage. There's a possibility (because DDR and DDR2 SODIMMs are
footprint compatible) to support the upcoming DDR2 modules in this
design too.

Now, there's a problem: DDR2 SDRAM supports the use of differential
signaling on data strobe lines (DQS). However, these signals are still
1.8V SSTL. Virtex-II Pro device (or maybe ISE software) seem not to
support differential SSTL IO.

So, the question is: do the specific hardware resources in Virtex-II
Pro exist to support DDR2 differential IO, or, if not, that are the
possible workarounds for this besides from just not using the DDR2
differential IO at all?

Regards,
Bob