A New Jersey truck driver pleaded guilty on Thursday to stealing the Francisco de Goya painting Children with a Cart while it was in transit and then later attempting to claim a $US50,000 ($58,000) reward.The US Attorney's Office in Newark says Steven Lee Olson, 54, pleaded guilty in federal court to conspiring to steal an object of cultural heritage.His accomplice - restaurant worker Roman Szurko, 27 - has pleaded guilty to the same charge.Prosecutors say the men broke into a truck that was carrying the Spanish artist's 1778 painting from the Toledo Museum of Art in Ohio to the Guggenheim Museum in New York. They later turned in the painting to claim the reward.The painting had been insured for $US1 million.Both men face a maximum prison time of five years.