(Reuters) - Futures tracking Wall Street's main stock indexes were marginally lower on Tuesday as investors refrained from making big bets ahead of the start of the Federal Reserve's March policy meeting.

All three major stock indexes finished higher in the previous session, with the Nasdaq bouncing back from two successive small weekly losses as growth stocks such as Alphabet and Tesla boosted the tech-heavy index.

Most megacap growth stocks were under pressure in premarket trading.

Investor darling Nvidia ( NVDA ) weakened 1.2% after the company unveiled the Blackwell B200, an AI chip it says is up to 30 times faster than its previous chip. Some investors suggested the news was priced into the high-flying stock.

Fellow chipmaker AMD dipped 2.5%, while semiconductor firms such as Marvell Technology, Intel and Broadcom also fell between 0.3% and 2.8%.

Super Micro Computer, which makes AI-optimized servers with Nvidia's ( NVDA ) chips, dropped 6.2% after the company filed for a stock shelf offering of up to 2 million shares.

At 7:00 a.m. ET, Dow e-minis were down 72 points, or 0.18%, S&P 500 e-minis were down 14 points, or 0.27%, and Nasdaq 100 e-minis were down 61.75 points, or 0.34%.

All eyes are on U.S. central bankers who are expected to hold rates steady at the end of their two-day meeting on Wednesday.

But, investors are concerned that their new economic projections may be a wild card, potentially signaling fewer interest rate cuts and a later start to the policy easing cycle.

Robust inflation data has pushed traders to pull back bets of the first rate cut coming in June to 55.2% from 71% at the start of last week, according to the CME FedWatch Tool.

"With price rises still steamier than expected, signs of a more watchful, wary Fed are likely to emerge from this meeting," said Susannah Streeter, head of money and markets, Hargreaves Lansdown.

"However, the wave of exuberance is continuing among investors still charged with enthusiasm about the seemingly infinite possibilities that artificial intelligence will bring to the corporate world."

Among other movers, crypto-exchange operator Coinbase Global and miners Riot Platforms and Marathon Digital Holdings shed between 4.1% and 6.0%, tracking the sharp slide in bitcoin.

Spire Global jumped 18.1% after the company announced a collaboration with Nvidia ( NVDA ) for AI-driven weather prediction.