June 11 (Reuters) - Wall Street's main indexes closed sharply higher on Thursday, with stocks extending gains after U.S. President Donald Trump called off planned attacks on Iran and on the eve of Elon Musk's SpaceX stock market debut.

Hours before the expected attacks, Trump said on the Truth Social platform that negotiations with Tehran had been referred to the highest levels of the Iranian leadership and had received the approval of a broad coalition of regional powers.

Oil prices fell sharply, while stocks extended their recovery from the previous session's sell-off. Major Wall Street indexes declined by more than 1% on Wednesday, with the tech-heavy S&P 500 confirming a correction.

Robert Phipps, a director at Bear Sterling Capital Management in Austin, Texas, said, "Our technical indicators show that there is a relative oversold condition here. Just as we rose too high and too fast, we have fallen too high and too fast."

Preliminary data showed the S&P 500 index rising 126.86 points, or 1.75 percent, to 7,393.85 at the close, while the Nasdaq Composite advanced 637.78 points, or 2.53 percent, to 25,801.47. The Dow Jones Industrial Average climbed 928.72 points, or 1.84 percent, to 50,847.50.

SpaceX on Thursday set pricing for the largest initial public offering in U.S. history at $135 a share, making Elon Musk's rocket and spacecraft maker one of the world's most highly valued companies.

The initial public offering raised an unprecedented $75 billion from the sale of 555.56 million shares, valuing the space, satellite and artificial intelligence services provider at $1.77 trillion, an unprecedented figure for an initial public offering.

SpaceX will thus rank seventh among US-listed companies when its shares begin trading on the Nasdaq index tomorrow, Friday, despite incurring losses last year and having revenues several times greater than those of other giant companies.

Trading in SpaceX shares is expected to begin tomorrow, Friday.

The S&P 500 has declined since hitting a record closing high in early June. The war in the Middle East has exacerbated inflationary pressures.