By David Shepardson WASHINGTON (Reuters) - Volkswagen AG has agreed to pay at least $1.22 billion to fix or buy back nearly 80,000 polluting U.S. 3.0 liter diesel-engine vehicles to settle claims it fitted illegal emissions-cheating software to the cars, court documents showed. German auto supplier Robert Bosch GmbH [ROBG.UL] also agreed to pay $327.5 million to U.S. diesel VW owners, according to the documents filed late Tuesday. Volkswagen could be forced to pay up to $4.04 billion if regulators don't approve fixes for all vehicles.