AT&T says new drive tests prove its 3G network is the fastest in the country.

The carrier says national drive tests from Global Wireless Solutions show AT&T's "nearest competitor" is 20 percent slower than AT&T's average national speeds, and its "largest competitor by subscriber count" runs 60 percent slower than AT&T's national average.

Verizon Wireless is the largest wireless operator in the country, making it the likely target of AT&T's second claim. T-Mobile USA claimed last spring that its HSPA+ network offered the nation's fastest 3G service, but has since changed its marketing to claim it operates the nation's "largest 4G network."

"We're very pleased with the nationwide results of GWS drive testing, which demonstrate that we're delivering a superior mobile broadband experience on a nationwide basis," said John Donovan, AT&T's chief technology officer, in a statement.  "Our top priority for the weeks and months to come is to continue our focus on network enhancements and improvements to ensure continued access to fast mobile broadband speeds and reliable voice service."

AT&T invested nearly $6 billion in wireless-related initiatives over the first three quarters of this year to help bump up the speed and reliability of its HSPA network.

GSW is a testing firm that compiles wireless network performance results covering more than 950,000 road miles in more than 400 U.S. markets representing about 88 percent of the U.S. population. The company's drive tests also indicated that 98.59 percent of voice calls connected over the AT&T network nationwide are completed without interruption, putting AT&T one-tenth of 1 percentage point, or one call in 1,000, from the only higher score in the industry.

Verizon claims its 3G network is the nation's largest and most reliable.