TULSA, Okla., Aug 3 -- McLeodUSA Inc. and Williams Communications Group Inc. have signed an agreement to allow each company's voice and data services to travel on the other's fiber optic network. Under the terms of the deal, Williams will allow McLeodUSA's voice and data services to travel over its fiber optic network in some of the largest markets in the United States. McLeodUSA, whose fiber optic network has focused on smaller cities, will in turn grant access to voice and data services to Williams. Financial terms of the agreement were not disclosed. Last month, Williams signed a similar agreement with KDDI Corp., Japan's second largest telecommunications carrier.