Mass 3D giveaway for film trailer

Letterman (centre) and Vernon (right) will watch the Super Bowl at home

About 150 million pairs of 3D glasses are to be given away in the US so TV viewers can watch a special film trailer during the Super Bowl final.

A 90-second preview of Dreamworks' animated movie Monsters vs Aliens will be broadcast on 1 February.

The glasses will be available from 28,000 shops across the country.

The film features the voices of Kiefer Sutherland and Reese Witherspoon, with a plot focusing on a group of monsters trying to prevent an alien attack.

Its directors - Rob Letterman, who was responsible for Shark Tale, and Conrad Vernon, known for Shrek 2 - also oversaw the trailer.

Letterman said the pair would be watching the event at home.

"We're going to test the effects of beer and 3D," he joked to the Associated Press.

The campaign would cost "tens of millions of dollars", Dreamworks said.

Viewers who do not have the glasses will still be able to see a "traditional" image on the screen when the commercial is shown.

NBC, the channel which broadcasts the Super Bowl final, has also scheduled a 3D episode of its comedy-drama series Chuck on 2 February.