WASHINGTON (MarketWatch) - The U.S. trade deficit jumped 13.3% to $39.1 billion in July, one month after it fell to the lowest level in almost four years, the Commerce Department said Wednesday. Economists polled by MarketWatch had projected the deficit would snap back to $39.0 billion in July on a seasonally adjusted basis. U.S. imports of petroleum, reflecting higher global prices, surged in July and demand for foreign-made autos and auto parts hit a record high. The value of goods imported into the U.S. rose 1.6% to $228.6 billion. Exports slipped 0.6% to $189.4 billion, as shipments of commercial planes, industrial engines and jewelry declined. Although the increase in imports suggests strengthening demand in the U.S., a larger trade gap usually means slower economic growth at home since America is buying more goods and services from other countries. Still, the U.S. trade gap is down 10% from one year ago, largely because the nation is producing and refining more petroleum for export. American exports of petroleum products set another record in July at $12.5 billion. The trade deficits with China and the European Union, which are unadjusted, were the highest on record. In June, the U.S. trade deficit had tumbled to $34.5 billion, which was the smallest gap since the fall of 2009.