Adds shares paragraph 4, analyst comment 7, detail throughout

By James Davey

LONDON, Aug 27 (Reuters) - JD Sports Fashion JD.L reported a steeper decline in second quarter underlying sales, reflecting weakness in the UK, though there were signs of stabilisation in its key U.S. market after a sharp decline in the previous quarter.

The sportswear retailer, which makes nearly 40% of its revenue in the United States through its JD Sports, Hibbett, DTLR and Shoe Palace stores, said like-for-like sales for its second quarter to August 2 fell 3.0%, having been down 2.0% in the first quarter.

Shares in FTSE 100-listed JD have lost a third of their value over the last 12 months, reflecting a market driven by discounts, a drop-off in demand for Nike NKE.N products, which account for about 45% of its sales, and uncertainty over the impact of U.S. President Donald Trump's tariffs on costs and consumer demand.

The stock was up 4% in early trading Wednesday.

The group said a 6.1% fall in like-for-like sales in the UK reflected a tough prior year comparison when trade was boosted by the men's Euro 2024 soccer tournament.

But it saw an improving trend in North America where like-for-like sales fell 2.3%, having been down 5.5% in the previous quarter, reflecting the deferral of several product launches from the first quarter, as well as stronger sales trends in apparel and online.

"We believe this is a better outcome than the market expected and is further vindication of strategy," analysts at Peel Hunt said.

JD forecast full-year 2025/26 profit before tax and adjusting items in line with current market expectations of 852 million pounds to 915 million pounds ($1.15-$1.24 billion), down from the 923 million pounds made in 2024/25.

That forecast is, however, before any indirect impact of U.S. tariffs which the group is continuing to work through.

"Across our regions and fascias, in general we see a resilient consumer, albeit very selective on their purchases. We therefore remain cautious on the trading environment going into H2," CEO Regis Schultz said.

JD also announced a new 100 million pound share buyback programme, which it said reflected its confidence in medium-term industry growth and ongoing market share gains.

($1 = 0.7402 pounds)

(Reporting by James Davey; Editing by Kate Holton and Sharon Singleton)

((james.davey@thomsonreuters.com))