HEMPSTEAD: Democrat Hillary Clinton accused Republican Donald Trump on Monday of having a long history of racist behavior during a heated presidential debate that could reshape the 2016 campaign for the White House.

Clinton and Trump interrupted each other throughout the debate on topics ranging from foreign policy to the economy. Trump said Clinton had very little to show for her many years in public life.

Clinton, a former secretary of state, and Trump, a real estate tycoon, slammed each other for the controversy stoked for years by Trump over whether President Barack Obama was born in the United States.

The president, who was born in Hawaii, released a long form birth certificate in 2011 to put the issue to rest. Only this month did Trump say publicly that he believed Obama was US-born.

“He (Trump) has really started his political activity based on this racist lie that our first black president was not an American citizen. There was absolutely no evidence for it. But he persisted. He persisted year after year,” Clinton said.

Trump repeated his false accusation that Clinton's failed 2008 presidential campaign against Obama had initiated the so-called “birther” issue.

“Nobody was pressing it, nobody was caring much about it ... I was the one that got him to produce the birth certificate and I think I did a good job,” Trump said.

African American voters overwhelmingly support Clinton, but Trump in recent weeks has said he believes his policy agenda would benefit them and said the policies of Obama and Clinton had failed to help black Americans.

He said Clinton's arguments were disingenuous.

“When you try to act holier than thou, it really doesn't work,” Trump said.

Clinton, 68, wore a red pantsuit, and Trump, 70, wore a dark suit and a blue tie to the encounter that could shift the course of the tight race for the Nov 8 election. She called him Donald, and he called her Secretary Clinton.

Charges of falsehoods

Each accused the other of distortions and falsehoods and urged viewers to check their campaign websites for the facts.

Clinton called the New York businessman's tax policies “Trumped-up trickle-down” economics and Trump accused the former secretary of state of being “all talk, no action.”

“I have a feeling I'm going to be blamed for everything,” said Clinton, the first woman to win the presidential nomination of a major US political party during one tough exchange.

“Why not?” retorted Trump, a real estate tycoon and former reality TV star making his first run at public office.

Clinton criticised Trump for not releasing his tax returns and said that decision raised questions about whether he was as rich and charitable as he has claimed to be. She noted that the few years of returns he had released showed that despite his wealth, he paid no federal income tax.

“That makes me smart,” Trump said.

“I have a tremendous income,” he said at one point, adding that it was about time that someone running the country knew something about money.

Clinton criticised Trump for failing to pay some of the business people with whom his company had contracted. She said she had met a lot of people who had been cheated by her opponent.

Trump said such incidents of non-payment had taken place when the work was unsatisfactory.

Trump attacked Clinton for her trade policies and said she would approve a controversial trade deal with Asian countries despite opposing it as a candidate.

“You were totally in favour of it, then you heard what I was saying, how bad it is, and you said, 'Well, I can't win that debate,' but you know that if you did win, you would approve that,” he said.

Clinton rejected the criticism.

“Well Donald, I know you live in your own reality, but that is not the facts,” she said.

Moderator Lester Holt struggled to rein in the candidates, with discussions about trade policy suddenly shifting to the fight against the militant Islamic State (IS) as Trump accused Clinton of giving away information to the enemy by revealing on her website how she planned to defeat the group. Clinton said that unlike Trump, she at least had a plan for fighting Islamist militants.

Tight race

Opinion polls have shown the two candidates in a very tight race, with the latest Reuters/Ipsos polling showing Clinton ahead by 4 percentage points, with 41 per cent of likely voters.

A second Reuters/Ipsos poll released on Monday showed half of America's likely voters would rely on the debates to help them make their choice. More than half, 61pc, were hoping for a civil debate and were not interested in the bitterness shown on the campaign trail.

Asian share markets recouped early losses on Tuesday and the dollar edged away from a one-month trough against the yen, suggesting investors judged Democrat Hillary Clinton was winning her debate against Republican Donald Trump.

Markets have tended to see Clinton as the candidate of the status quo, while few are sure what a Trump presidency might mean for US foreign policy, trade and the domestic economy.

The size of the television-viewing audience was expected to challenge the record of 80 million Americans who watched 1980's encounter between Democratic President Jimmy Carter and Republican Ronald Reagan.

Some commentators forecast Super Bowl-sized viewership of about 100 million people.

By contrast with the single-party debates held during the Republican and Democratic state nominating contests, the audience was asked to remain silent and not applaud or respond to the candidates' remarks.

Least liked

Both Trump and Clinton, shown in opinion polls to be the least liked White House candidates in modern history, hoped to use the debate to erase lingering voter doubts and address campaign-trail weaknesses.

The stakes are enormous. Clinton once had a sizable lead, but that has evaporated amid more questions about her family's foundation and use of a private email server while secretary of state under President Barack Obama.

If the election were held today, Clinton would still defeat Trump, with an 88pc chance of reaching the 270 electoral college votes needed, according to the Reuters/Ipsos States of the Nation project, which is based on a weekly online tracking poll of more than 15,000 Americans.

Two other presidential candidates — Libertarian Gary Johnson and Green Party candidate Jill Stein — were not invited to take part in the debate because neither had obtained at least 15pc support in national polls, the threshold established to qualify.