Time Warner Inc. could possibly delay until August 2000 the pending $58 billion AT&T Corp. merger with MediaOne Group, according to a proxy filed last week with the Securities and Exchange Commission. Time Warner and MediaOne are partners in Time Warner Entertainment, which consists mostly of Time Warner's cable systems. MediaOne also had a no-competition agreement with Time Warner. In light of AT&T's pending acquisition of MediaOne, MediaOne gave up its management rights in TWE and announced the end of its no-competition policy. Time Warner maintains that the AT&T-MediaOne merger cannot take place until a year after MediaOne gave up its TWE management rights - which happened August 3 - unless Time Warner gives its permission.