U.S. import prices rose by a slightly larger-than-expected 1.3 percent in August, Labor Department (search) data showed on Friday, as petroleum prices leapt again. But other import costs remained subdued.

Wall Street had forecast a 1.2 percent increase in the price of imported goods, which are monitored as an early warning of inflation and will worry the Federal Reserve (search) if it thinks these cost pressures will subsequently show up in consumer prices.

Economists are also scrutinizing data for evidence of how Hurricane Katrina (search) has hurt U.S. growth. But the Labor Department said the August survey was conducted before the storm struck and therefore was not affected by Katrina.

July's import price numbers were revised down to show a 0.8 percent gain from 1.1 percent previously reported.

Excluding petroleum, import prices were flat compared with a 0.2 percent fall in July and have shown no increase since they rose 0.4 percent in April, the Labor Department said.

Over the last 12 months, import prices have risen 7.6 percent, reflecting a 42.5 percent rise in the cost of petroleum, which has challenged consumer spending power and raised concern at the U.S. central bank about inflation.

The Fed is monitoring the pass-though of energy prices into core measures of inflation and has said that while there has been some spill-over, long-term inflation expectations remain well-contained so far.

The cost of imported food and beverages fell 0.1 percent in August while the cost of nonpetroleum industrial supplies was up just 0.2 percent. Auto import prices were unchanged for the second straight month. Prices for capital goods also held steady, while the price of consumer goods, excluding autos, declined by 0.2 percent.

Export prices were down 0.1 percent, compared with forecasts for a 0.2 percent increase and a 0.1 percent rise in July.