After terminating a deal with 4Kids, an independent producer of children’s programming, the Fox network closed down its Saturday morning block of cartoons on Monday, and became the first major broadcast network to agree to sell a part of its schedule to producers of infomercials.

Fox executives said that children’s programming was simply no longer viable on network television — mainly because of competition from cable channels.

All the other broadcast networks still have children’s programming on Saturday mornings. One, the CW network, has a deal with 4Kids that is similar to the arrangement with Fox. As part of an agreement between Fox and 4Kids, the deal will be terminated as of January. The news was first reported by the trade publication Variety on Monday.

Fox is giving two hours of Saturday time back to its affiliated stations.