WASHINGTON (Reuters) - Initial claims for U.S. jobless benefits fell last week but the number of unemployed workers on the benefit rolls a week earlier hit a level not seen since the aftermath of the attacks of Sept. 11, 2001, the government said on Thursday.

First-time filings for unemployment aid dipped 13,000 in the week ended May 10 to a seasonally adjusted 417,000 from a revised 430,000 in the prior week, the Labor Department said.

Wall Street economists polled by Reuters expected claims to hold steady at the 425,000 level originally reported for the May 3 week. The latest drop marked the second consecutive weekly decline in initial claims and brought the four-week moving average, a more reliable labor-market barometer that smoothes weekly fluctuations, down by 7,500 to 439,750, its lowest level in a month.

However, the number of jobless workers who remained on the benefit rolls in the May 3 week, the latest week for which data are available, rose a sharp 120,000 to 3.77 million. That marked its highest level since the middle of November 2001, when the U.S. economy was reeling from the Sept. 11 attacks.

The report showed initial claims above the key 400,000 level for the 13th week in a row. Economists say claims above 400,000 indicate a stagnant labor market.