US STOCKS-Wall Street indexes rally after Trump postpones strikes on Iran's power plants

By Sinéad Carew and Purvi Agarwal

March 23 (Reuters) - The three main U.S. stock indexes finished Monday's session up more than 1% as oil prices fell after President Donald Trump said he had ordered the military to postpone strikes against Iranian power plants following "productive conversations" with Tehran.

However, Iran's Parliamentary Speaker Mohammad Baqer Qalibaf posted on social media that no talks had been held with the U.S., contradicting Trump's announcement that there were talks between the United States and Iran in the past day in which the two sides had "major points of agreement" and that a deal could be done soon to settle the war.

While U.S. equities fell last week, they staged a sharp recovery on Monday after Trump's comments sent oil prices lower. Equities had been trading lower earlier in the day after threats of attacks on Israeli and Iranian power networks.

"You never know who to believe but it does appear that Trump is trying to start discussions with somebody in Iran to resolve the war despite strong denials from Iran. This has caused significant optimism in stock prices today with the market up strongly although off its highest levels because of the Iranian denials," said Tim Ghriskey, senior portfolio strategist at Ingalls & Snyder in New York.

With oil prices settling down more than 10% on Monday Wall Street's 3 main stock indexes registered their biggest single-day percentage gains since February 6.

The Dow Jones Industrial Average .DJI rose 631.00 points, or 1.38%, to 46,208.47 while the S&P 500 .SPX gained 74.52 points, or 1.15%, to 6,581.00 and the Nasdaq Composite .IXIC gained 299.15 points, or 1.38%, to 21,946.76.

The CBOE Volatility Index .VIX, Wall Street's fear gauge, retreated after earlier hitting 31.04, which its highest level in two weeks. The index pared some losses to end down 0.63 points at 26.15.

All of the S&P 500's 11 major industry sectors advanced with big gains in cyclical sectors such as consumer discretionary .SPLRCD, which finished up 2.46%, while defensive sectors were weaker with healthcare .SPXHC finishing barely higher and consumer staples .SPLRCS closing up 0.37%.

"The volatility is likely to continue and it's all about the price of oil. Nothing else really matters to people in the short term. So when oil prices are down, stocks go up and vice versa," said Bob Doll, chief investment officer at Crossmark Global Investments. "What's up the most today is not a surprise. It's things with economic sensitivity."

Meanwhile, investors trimmed bets for an interest-rate hike from the U.S. Federal Reserve to a roughly 13% probability for December from just above 25% in the prior session, according to CME Group's FedWatch.

Traders were betting on a roughly 72% chance that rates would be unchanged by year end after scaling back bets for cuts last week after the central bank struck a hawkish tone due to concerns about higher inflation.

With that, the small-cap Russell 2000 .RUT outperformed large-cap indexes on Monday to finish up 2.3%. On Friday, the index, which is sensitive to higher interest rates, had ended more than 10% below its record close of January 22, confirming it had been in correction territory.

Shares rallied in airlines, which are hugely sensitive to the price of oil because of jet fuel costs. Alaska Air ALK.N and United Airlines UAL.N shares both rose more than 4% while American Airlines AAL.N added 3.66%. Shares in cruise ship operators soared with Norwegian Cruise Line .NCLH.N adding more than 6% while Carnival Corp .CCL.N and Viking Holdings .VIK.N both climbed more than 5%.

Banks, which had weakened during the conflict, gained ground on Monday with the S&P 500 Banking index .SPXBK adding more than 1% to record its biggest daily gain since February 25. JPMorgan Chase JPM.N added 1.2% while Goldman Sachs GS.N rose 2.2%.

Investors will look forward to Fed speakers, business activity surveys and consumer sentiment readings this week.

In individual stocks, Synopsys SNPS.O rallied 2.9% after Reuters reported that activist investor Elliott Investment Management has amassed a multibillion-dollar investment in the electronic design automation firm.

Advancing issues outnumbered decliners by a 3.6-to-1 ratio on the NYSE where there were 59 new highs and 109 new lows. On the Nasdaq, 3,546 stocks rose and 1,229 fell as advancing issues outnumbered decliners by a 2.89-to-1 ratio.

The S&P 500 posted 7 new 52-week highs and 8 new lows while the Nasdaq Composite recorded 34 new highs and 154 new lows.

On U.S. exchanges about 20.94 billion shares changed hands compared with the moving average of 20.68 billion for the last 20 sessions.