By Susan Heavey

WASHINGTON (Reuters) - U.S. Republican presidential candidate Donald Trump on Tuesday brushed off billionaire investor Warren Buffett's blistering critique of his business acumen.

"I don't care much about Warren Buffett," Trump said on the FOX Business television network Tuesday morning, a day after Buffett lashed out at Trump in a speech at a campaign rally for Democratic candidate Hillary Clinton.

Buffett, a widely followed investor who is chairman and chief executive officer of Berkshire Hathaway Inc, scorned Trump's 1995 move to list Trump hotels and casino resorts on the New York Stock Exchange, saying it lost money for the next decade and that "a monkey" would have outperformed Trump's company.

He also challenged Trump to release his tax returns, something the real estate mogul and television star has declined to do so far citing an Internal Revenue Service audit.

Trump, who has held up his career in business as a qualification to lead the country, defended his record running his hotel and casino business in Atlantic City, New Jersey.

"I had great timing. I got out," after seven years, he told FOX Business on Tuesday. "I took a lot of money out of Atlantic City, which is what I'm supposed to do. I'm a businessperson."

Trump said he "did well in the good times in Atlantic City, but then times started going very bad."

Trump said he used to invest in U.S. stocks but got out because "I don't like what I'm seeing at all," pointing to U.S. immigration policies, Syrian refugees and what he said were "artificially low" interest rates.

He also vowed to spend twice as much on U.S. infrastructure as Clinton, who has pledged $275 billion on rebuilding the nation's crumbling roads and bridges, among other structures.

Trump, who has been criticized by fellow Republicans and others for responding too readily to opponents, declined to target Buffett personally for his comments: "There's no counter-punch."

Buffett on Monday vowed to do "whatever it takes" to get out the vote in his congressional district in Nebraska, including driving voters himself to the polls to cast ballots.

With Clinton by his side, Buffett told the crowd that his "final straw" was Trump's critical response to the Muslim parents of a decorated U.S. soldier killed by a bomb in Iraq 12 years ago.

Buffett is No. 3 on Forbes magazine's list of the richest billionaires, with a net worth calculated at $60.8 billion.

(Additional reporting by Amanda Becker in Omaha and Emily Stephenson; Writing by Susan Heavey; Editing by Richard Valdmanis and David Gregorio)