May 20 (Reuters) - Wall Street's main indexes closed more than 1 percent higher on Wednesday, recovering from a three-day sell-off, boosted by improved sentiment thanks to shares of technology and chip companies, which rose ahead of Nvidia's quarterly results announcement.

Investors are awaiting the latest report from Nvidia, the world's leading and most valuable artificial intelligence chip maker, to confirm that the appetite for spending on AI remains strong enough to support high valuations in the technology sector.

The Philadelphia Semiconductor Index rose sharply ahead of the report's release, with several companies posting significant gains.

Carol Schleif, senior economist at BMO Private Wealth in Minneapolis, said, "Technology is driving the market again today, along with the theme of artificial intelligence. We've put yesterday's worries about rising interest rates and potential inflation behind us, and are leaning more toward the AI in everything story."

She added, "It's a bit unusual, actually, because you'd expect the market to remain fairly quiet while awaiting Nvidia's results later today. But there's clearly a lot of optimism."

The failure to reach a solution to the US-Israeli war on Iran has led to a decline in US indices over the past three days, as investors worried that rising oil prices would increase inflation enough to prompt the Federal Reserve (the US central bank) to raise interest rates.

According to preliminary data, the Standard & Poor's 500 index rose by 79.06 points, or 1.08 percent, to close at 7432.67 points, while the Nasdaq Composite index climbed by 398.33 points, or 1.54 percent, to reach 26269.04 points.

The Dow Jones Industrial Average rose 647.44 points, or 1.31 percent, to 50,011.32.