The prices of goods imported into the United States rose much more than expected in May as oil costs posted the largest increase since early 2003, a government report showed on Thursday.

Import prices were up 1.6 percent, notching the biggest one-month rise since February of last year and the eighth consecutive monthly advance, after a revised 0.2 percent gain in April, the Labor Department (search ) said.

The rise was double the 0.8 percent increase Wall Street analysts had anticipated and signal an increase in inflation in the U.S. economy. Higher price pressures have fueled expectations policy-makers will move sooner rather than later to raise interest rates.

Import prices rose 0.2 percent the previous month.

The cost of petroleum product imports surged 10.3 percent after falling a revised 0.4 percent in April. Excluding petroleum, import prices rose 0.4 percent in May.

Export prices rose 0.3 percent compared with an upwardly revised 0.7 percent in April, the ninth straight monthly increase.

Imported food costs fell 0.3 percent after climbing 1.2 percent the previous month.

Industrial supplies, excluding petroleum, rose 2.1 percent, with prices for iron and steel, natural gas and lumber all contributing to the gain.

Over the past 12 months, the price index for petroleum imports was up 43.9 percent, while overall import prices rose a more modest 7.0 percent.