Harley-Davidson Inc said on Thursday that quarterly earnings fell 37 percent, pulled down by costs from its recession-triggered restructuring as well as a tax change in its home state of Wisconsin.

But the motorcycle maker affirmed its full-year shipment outlook and said it was mildly encouraged that the rate at which sales declined in the United States, its biggest market, slowed during the quarter.

Even so, Harley-Davidson, which has already laid off 20 percent of its workforce and closed several plants, said its cost-cutting efforts would continue and that another 300 to 400 jobs would be eliminated over the next two years. It said costs from the continuing revamp could reach $150 million over the next two years.

The company reported first-quarter net income of $117.3 million, or 50 cents a share, down from $187.6 million, or 79 cents a share, a year earlier.

Total sales, which includes parts and accessories, slipped about 1 percent to $1.29 billion. But sales of its iconic bikes, which account for the lion's share of its revenue, fell 12 percent, pulled down by 17.2 percent decline in Canadian sales.

The company affirmed its plans to ship between 264,000 and 273,000 Harley-Davidson motorcycles to dealers worldwide in 2009.

(Reporting by James Kelleher; Editing by Lisa Von Ahn)