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NEW YORK, Sept 30 (Reuters) - U.S. stocks closed solidly higher on Wednesday as government leaders continued talks for a new pandemic relief package and positive economic data helped the major indexes end the third quarter in positive territory.

All three major indexes surged after U.S. House of Representative Speaker Nancy Pelosi and Treasury Secretary Steven Mnuchin both expressed hope for a breakthrough in partisan stimulus negotiations.

The indexes pared gains after Senate Majority Leader Mitch McConnell warned the sides remain "far apart" in their talks.

"We had the economic news which was pretty good, and continued discussions with Mnuchin and Pelosi drove hopes that we could have stimulus before the election before McConnell threw cold water on it," said Paul Nolte, portfolio manager at Kingsview Asset Management in Chicago.

"Volatility has been the watchword all month and I don't think we're out of the woods yet," Nolte added.

Market participants also were digesting Tuesday's contentious presidential debate, where President Donald Trump and Democratic challenger Joe Biden talked over each other and traded insults as they sparred over the COVID-19 pandemic, healthcare and the economy.

A spate of economic data mostly surprised to the upside, with ADP National Employment index blowing past analyst expectations and pending home sales surging to an all-time high.

The major indexes wrapped up September with their first monthly declines since March, when mandated shutdowns slammed the economy. But they posted gains for the third quarter and their largest two-quarter winning streaks in years.

Unofficially, the Dow Jones Industrial Average rose 393.25 points, or 1.43%, to 27,845.91, the S&P 500 gained 34.76 points, or 1.04%, to 3,370.23 and the Nasdaq Composite added 105.49 points, or 0.95%, to 11,190.74.

Nikola Corp stock soared after Chief Executive Mark Russell said he was close to a deal with an energy partner and defended the company against a short-seller's fraud allegations.

Micron Technology Inc said it has not yet obtained new licenses needed to sell memory chips to China's Huawei Technologies Co Ltd, sending its shares lower.

Duke Energy Corp stock jumped after the Wall Street Journal said the company had been approached by peer NextEra Energy Inc regarding a possible takeover. (Reporting by Stephen Culp; Editing by David Gregorio)