Fox Broadcasting Co., buoyed by $400,000 in profits during the past six months, announced it will expand its prime-time TV programming next fall from two nights to three.

Fox officials said that programs on Monday evening would be added to its weekend lineup beginning Sept. 11. The announcement came at the close of the network's annual affiliates convention here."Fox has come a long way in two years," said Michael Fisher, chairman of the network's Board of Governors. "We are undeniably a force to be reckoned with in the industry."

Fox challenged NBC, ABC and CBS with its Saturday and Sunday evening programming that includes the popular "America's Most Wanted," "The Tracey Ullman Show," "It's Garry Shandling's Show" and "Married . . . With Children."