As ratings continued to fall for ABC's World News Tonight , ABC News chief David Westin announced Tuesday that Charles Gibson would become the sole anchor of the program next Monday, replacing Elizabeth Vargas and BOB WOODRUFF, who had been named co-anchors in January. Woodruff was seriously injured in Iraq a few weeks later, leaving Vargas as the de facto sole anchor ever since. After taking a maternity leave, Vargas will return to the network in the fall, continuing to co-anchor the network's magazine show, 20/20, with John Stossel. In an interview with today's (Wednesday) New York Times , Gibson observed, "I am to some extent a creature of circumstance to horrendous events," referring to the death last year of Peter Jennings and Woodruff's injury. In a separate interview on ABC's website, Gibson attributed his ascension to events that had "conspired to derail an experiment here." Gibson will remain on Good Morning America with Diane Sawyer through next month. The Times said that three other ABC News personalities are expected to be showcased on the morning show after Gibson's departure Bill Ritter, an anchor on WABC-TV in New York, who occasionally contributes to 20/20 ; Bill Weir, a co-anchor of the weekend GMA , and Chris Cuomo, co-host of ABC's Primetime.