AT&T’s (T) 3G network is almost done. Like 73% complete as of today. Nearly totally covered, well except for the 27% that will be finished later this year that is.

Just weeks away from the hotly anticipated launch of Apple’s (AAPL) 3G iPhone, AT&T – the exclusive telco sales partner to Apple in the U.S. – says next month “six remaining markets” will get a 3G network upgrade. The company goes on to say that it has 3G in 275 markets and “by year-end, the AT&T 3G network will be available in nearly 350 markets.”

Don’t be confused, be reassured. If you buy a hot new 3G phone from AT&T, it will certainly zip along at top network speeds as long as you aren’t trying to use it in those markets where it isn’t yet available.

Apple is expected to introduce the sleeker, faster iPhone early next month and start selling the phone by the end of June. AT&T is under the gun to get the entire network up to speed so its coveted iPhone users don’t flood the customer service department with complaints about inadequate 3G connections and broken promises.