WASHINGTON, April 14 (Reuters) - U.S. import prices rose more than expected in March, lifted by higher costs for petroleum products and tight supply chains, the latest indication of inflation heating up as the economy reopens. The Labor Department said on Wednesday import prices increased 1.2% last month after advancing 1.3% in February. Economists polled by Reuters had forecast import prices, which exclude tariffs, increasing 1.0%. (Reporting By Lucia Mutikani; Editing by Catherine Evans)