By Arselia Gales

AT&T just ran a full-page attack ad in the New York Times, the Wall Street Journal and USA Today with claims that T-Mobile drops twice as many calls and its network speeds are only half as fast as AT&T’s.

You surely recall that the two carriers had agreed to merge in 2011 before regulators put the kibosh on what would’ve been a super-carrier. That forged peace seems to be all but gone now, with the tension between two building over the past couple of months.

Mobile operators cracking on each other in ads isnt anything new,” said Yankee Group senior analyst Rich Karpinski. “Certainly, attacking the No. 4 market share player in any market is a bit unusual. T-Mobile must be pleased that it is at least stirring the ire of its larger rival. With T-Mobile driving prices down, more premium-priced competitors will certainly want to turn the discussion to other issues, such as network quality.”

Karpinski also noted that since U.S. operators are becoming very similar when it comes to network speeds and device availability, differentiation will come via pricing, service offers, market-by-market network differences and effective advertising.

“As T-Mobile sets to unveil its uncarrier marketing strategy this year, look for its fellow still-carriers to bite back, and hard.”