WASHINGTON (Reuters) -U.S. wholesale inventories increased slightly less than initially estimated in March amid decreases in the stocks of electrical, lumber, apparel and farm products.

Stocks at wholesalers rose 0.4%, revised down from the 0.5% gain estimated last month, the Commerce Department's Census Bureau said on Thursday. Economists polled by Reuters had expected the rise in inventories would be unrevised.

Inventories, a key part of gross domestic product, advanced 0.5% in February. They rose 2.2% on a year-on-year basis in March. Businesses front-loaded imports in the first quarter, seeking to avoid President Donald Trump's sweeping duties on foreign goods, resulting in a large trade deficit.

Most of the imports ended up as inventory.

The government's advance gross domestic product estimate for first quarter published last week estimated that business inventories increased at a $140.1 billion annualized rate after rising at only a $8.9 billion pace in the October-December quarter. Inventories added 2.25 percentage points to GDP, the most since the fourth quarter of 2021.

That was, however, insufficient to offset the drag from the trade gap. Trade sliced off a record 4.83 percentage points from GDP, resulting in the economy contracting at a 0.3% rate, the first decline in three years. The economy grew at a 2.4% pace in the fourth quarter.

Sales at wholesalers increased 0.6% in March after rising 2.0% in February. At March's sales pace it would take wholesalers 1.30 months to clear shelves, unchanged from in February.

(Reporting by Lucia Mutikani)