Viacom Inc. and NBC Universal are cutting a combined 1,350 positions worldwide as the recession slows advertising sales and movie revenue.

Viacom said Thursday it is cutting 850 jobs, or 7 percent of its work force, and will take up to $450 million in fourth-quarter asset write-downs. General Electric Co.’s NBC Universal unit told its staff it will eliminate 500 positions, or 3 percent.

Most of Viacom’s cuts will be at MTV Networks, according to media reports quoting sources that say as many 500 jobs may be affected. Paramount Pictures also will see cuts.

Many of NBC’s layoffs are expected to be in its news division, including at least seven positions at its Los Angeles bureau. At Universal Pictures, some 70 people were cut worldwide.