By Sinéad Carew and Bansari Mayur Kamdar

(Reuters) -Wall Street's major indexes closed higher on Tuesday after shares in hotshot chipmaker Nvidia shook off early losses and investors looked ahead to the Federal Reserve's policy meeting conclusion on Wednesday for clues on interest rate policy.

Shares in Nvidia pulled out of the red after it revealed pricing and shipment plans for its hotly anticipated Blackwell B200 artificial intelligence chip, which it says could be 30 times faster than current chips.

Michael James, managing director of equity trading at Wedbush Securities in Los Angeles attributed Tuesday's overall gains to improving sentiment after Nvidia's shares turned around along with ongoing bullishness about the economy's direction.

"You're continuing to see money go into the market and not just technology," said James. "It certainly helps when you're seeing the large cap tech names today like Nvidia show relative strength from where they opened. But it's continuing the overall bullish theme that's been going on since the year started."

According to preliminary data, the S&P 500 gained 27.88 points, or 0.54%, to end at 5,177.30 points, while the Nasdaq Composite gained 63.34 points, or 0.39%, to 16,166.79. The Dow Jones Industrial Average rose 320.36 points, or 0.83%, to 39,110.79.

Investors were also preparing a day ahead of the Fed's policy update, including a press conference from Chair Jerome Powell. Robust inflation data has pulled back bets for the first rate cut in June to about 59% from about 69% at the start of last week, according to the CME FedWatch Tool.

"There's optimism that the Fed's not going to surprise us a lot on Wednesday," said Gene Goldman, chief investment officer at Cetera Investment Management. "We think three cuts are still on the table."

But, Goldman still sees Powell reminding the market that he is cautious about inflation and that policy will depend on economic data and expects the central bank to update its inflation and economic growth projections.

Among other movers, crypto-exchange operator Coinbase Global and miners Riot Platforms and Marathon Digital Holdings fell along with a slide in bitcoin.

MicroStrategy shares sank after the company announced it had completed a $603.75 million convertible debt offering - its second in a week - to fund bitcoin purchases.

AI server maker Super Micro Computer shares tumbled after it announced it will sell 2 million shares that could fetch about $2 billion.

Spire Global shares soared after it announced a collaboration with Nvidia for AI-driven weather prediction.

(Reporting by Bansari Mayur Kamdar and Shashwat Chauhan in Bengaluru; Editing by Savio D'Souza, Maju Samuel and Aurora Ellis)