A simmering feud between General Motors Co and Ford Motor Co heated up on Sunday as Ford objected to GM's Super Bowl advertisement for its Chevy Silverado pickup truck.

The ad, which will run on NBC's television broadcast of the Super Bowl on Sunday, depicts an apocalyptic scene in which Chevrolet Silverado pickup trucks and their owners escape death and make it to a pre-arranged meeting point.

But, one of their friends, identified as Dave, who drives a Ford, doesn't make it to the meeting site, in the video that plays off the idea that the ancient Mayans predicted the world would end in 2012.

A letter from Ford attorney Lynne M. Matuszak says that according to insurance industry data it is Ford, and not GM, that makes the safer pickup truck and she called on GM not to use the ad. GM has refused to pull the spot.

GM has had the advertisement on its website for a few days, and a posting on YouTube by Sunday afternoon had been viewed 1.6 million times. GM stands by the ad and its claims.

Ford insists that Chevrolet refrain from running the commercial during (Sunday's) Super Bowl; refrain from any future use of the commercial; and permanently remove the commercial from its website, its YouTube and Facebook pages and any other Internet sites, Matuszak wrote.

Jim Farley, Ford's global sales and marketing chief, told reporters on sidelines of the National Automobile Dealers Association convention in Las Vegas on Sunday that despite the GM claim that pickup truck registrations over the past 30 years support the ad's claim, Ford will fight the commercial.

We've been the leader in the truck market and the best-selling vehicle for 35 years. So from an advertising standpoint, we will absolutely defend our leadership in the market. Any claims related to that, said Farley.

The letter was really intended to challenge the assertion towards that kind of claim, said Farley.

The skirmish is the latest in a series of jabs Ford and GM have lobbed at each other in the past year.

Last summer, in the run-up to a book on Ford by Bill Vlasic of the New York Times, Farley was quoted as saying he hates GM and what it stands for.

I'm going to beat Chevrolet on the head with a bat. And I'm going to enjoy it, Farley is quoted as saying.

Last Friday in Las Vegas, at a J.D. Power auto industry event, Alan Batey, head of Chevrolet sales for GM, responded to Farley's jab.

It's interesting because Farley uses the analogy of using a baseball bat, said Batey who has lived in Britain and Australia. Well, where I come from, you use cricket bats and they are like three times bigger. So, I actually favor my chances on that one.

(Reporting By Bernie Woodall; Editing by Tim Dobbyn)

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