US STOCKS-Wall St futures decline as tariff uncertainty curbs risk appetite

For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window.

Updates prices throughout, adds details

By Shashwat Chauhan and Ragini Mathur

Feb 23 (Reuters) - U.S. stock index futures slipped on Monday as renewed tariff uncertainty unnerved investors after President Donald Trump announced a new 15% duty following a Supreme Court ruling that struck down his broader levies.

The Supreme Court, in a 6-3 ruling on Friday, voided most of the tariffs Trump imposed last year, finding that the emergency law he relied on did not allow the imposition of tariffs.

Using a different statute, Trump announced first a 10%, then a 15%, global levy that could last five months while the administration searches for more durable workarounds.

"It's really hard from a business standpoint when you are at a company to know how do you plan if you're not even sure about suppliers, supply chains and what the tariffs are going to look like," said Arthur Laffer Jr., president of Laffer Tengler Investments.

"That's a huge concern for corporate America and why it was really important to get that hammered out and ironed out as fast as possible, so that companies know what the playing field really looks like, and they can plan accordingly."

All three main stock indexes clocked weekly gains on Friday as markets took the Supreme Court's decision in stride, with the Nasdaq .IXIC snapping a five-week losing streak.

At 07:00 a.m. ET, Dow E-minis YMcv1 were down 162 points, or 0.33%, Nasdaq 100 E-minis NQcv1 were down 129 points, or 0.51%, and S&P 500 E-minis EScv1 were down 23.75 points, or 0.34%.

Most megacap and growth stocks were lower in premarket trading, though Alphabet GOOGL.O bucked the trend with a 0.3% gain after rising around 4% on Friday.

Nvidia NVDA.O inched 0.1% lower ahead of quarterly earnings due on Wednesday, with the tech-heavy U.S. markets facing a major test as commentary from the world's largest company by market capitalization could offer key insight about the AI sector that has been hit by growing investor skepticism.

High stock valuations and AI disruption fears have lately pressured technology and other sectors, as investors question if massive AI spending is paying off.

Earnings from major software firms including Salesforce CRM.N and Intuit INTU.O will be on the radar later this week, given that the S&P 500 software and services index .SPLRCIS has slumped more than 20% this year amid growing AI disruption fears.

Among other movers on Monday, Eli Lilly LLY.N rose 3.2% after rival Novo Nordisk's NOVOb.CO obesity drug fell short against Lilly's drug in a Copenhagen trial.

Merck MRK.N edged 1% higher after the drugmaker said it will split its human-health business into two divisions.

Domino's Pizza DPZ.O climbed 4.5% after the fast-food chain beat Wall Street estimates for fourth-quarter U.S. same-store sales.

Cryptocurrency and blockchain-related stocks dropped as bitcoin BTC= lost around 2%, with exchange operator Coinbase Global COIN.O and crypto hoarder Strategy MSTR.O falling more than 2% each.

Gold and silver miners were broadly higher as prices of both precious metals gained. Top gold miner Newmont NEM.N climbed 1% while silver miner Hecla Mining HL.N added 2%.

(Reporting by Shashwat Chauhan and Ragini Mathur in Bengaluru; Editing by Devika Syamnath)

((Shashwat.Chauhan@thomsonreuters.com;))