AT&T this afternoon disputed a new advertisement in which T-Mobile USA spoofs AT&T and its partner Apple, and lays claim to the nation's largest 4G network.

But rather than questioning whether the HSPA+ mobile standard qualifies as 4G, or challenging the ad's portrayal of AT&T's network as a middle-aged man riding on the back of a customer, AT&T says its own HSPA+ network is actually larger than T-Mobile's HSPA+ network.

Here's the statement issued by AT&T about the T-Mobile ad, which can be viewed above.

T-Mobile's claims about 4G are based on the same HSPA+ technology we have deployed to 180M people today, more than T-Mobile’s reported 140M, and we’ll have it rolled out to 250M people by the end of this month, substantially more than the 200M T-Mobile says it will have by year-end.

Now that our HSPA+ speed upgrade is underway, we’re focused on the next upgrade to make our fastest network even faster – and that’s LTE, which we’re trialing now and will launch in 2011.

We've asked T-Mobile if it has any comment on the AT&T statement, and we'll update this post depending on the response.