WASHINGTON, Feb 14 (Reuters) - A federal judge on Tuesday granted preliminary approval to a Volkswagen AG settlement to pay at least $1.22 billion to fix or buy back nearly 80,000 polluting U.S. 3.0 liter diesel-engine vehicles.

Separately, U.S. District Judge Charles Breyer in San Francisco also agreed at a court hearing to grant preliminary approval to German auto supplier Robert Bosch GmbH's settlement to pay $327.5 million to U.S. diesel VW owners.

Volkswagen could be forced to pay up to $4.04 billion if regulators don't approve fixes for all vehicles. Breyer will hold a May 11 hearing on whether to grant final approval. (Reporting by David Shepardson in Washington; Editing by Cynthia Osterman)

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