Los Angeles ? Negotiations between striking Hollywood writers and studios collapsed Friday, the culmination of a day in which the sides traded barbs and accusations.

The Alliance of Motion Picture and Television Producers announced that the round of talks that started on Tuesday had broken down, stalling efforts to end the five-week-long strike that has sidelined many prime-time and late-night television shows.

The alliance said it was “puzzled and disheartened” by the Writers Guild of America’s ongoing negotiating strategy “that seems designed to delay or derail talks rather than facilitate an end to this strike.”

In response, the guild said the chief alliance negotiator slammed the door on bargaining after presenting an ultimatum and before the union could respond to his latest proposal regarding crucial new-media compensation issues.