Donald Trump has sought to pin America's economic and national security problems on Hillary Clinton after finding himself on the defensive for much of the first US presidential debate.

The Republican nominee belittled the former US senator and secretary of state as a "typical politician" incapable of delivering the change many Americans crave.

Mr Trump also accused moderator Lester Holt of a left-leaning performance and going harder on him than Mrs Clinton - even floating the theory that organisers had intentionally given him a faulty microphone to set him up.

Read more: The Midge - Some of the choicest cuts from the first live television debate between Hillary Clinton and Donald Trump

Democratic nominee Mrs Clinton was thoroughly prepared in the debate, not only with detailed answers about her own policy proposals, but also sharp criticism of Mr Trump's business record, his past statements about women, and his false assertions that president Barack Obama may not have been born in the United States.

She said his charges about Mr Obama were part of the Republican hopeful's pattern of "racist behaviour."

The Democrat also blasted Mr Trump for his refusal to release his tax returns, breaking with decades of presidential campaign tradition. She declared: "There's something he's hiding."

Mr Trump has said he cannot release his tax returns because he is being audited, though tax experts have said an audit is no barrier to making the information public.

When Mrs Clinton suggested her rival's refusal may be because he paid nothing in federal taxes, he interrupted to say: "That makes me smart."

The debate was confrontational from the start, with Mr Trump frequently trying to interrupt Mrs Clinton and speaking over her answers.

Mrs Clinton was more measured and restrained, often smiling through his answers, well aware of the television cameras capturing her reaction.

"Hillary told the truth and Donald told some whoppers," the Democrat hopeful's running mate, Tim Kaine, told ABC News.

Mr Trump's criticism of Mrs Clinton turned personal in the debate's closing moments.

He said: "She doesn't have the look, she doesn't have the stamina (to be president)."

Mrs Clinton leapt at the opportunity to remind voters of Mr Trump's controversial comments about women, who will be crucial to the outcome of the November election.

Read more: The Midge - Some of the choicest cuts from the first live television debate between Hillary Clinton and Donald Trump

"This is a man who has called women pigs, slobs and dogs," she said.

Mr Trump later responded to a reference in the debate to his comments about a 1996 Miss Universe winner who was said to have gained weight after she won the beauty pageant which he formerly owned.

Donald Trump said it was a "real problem" when Alicia Machado gained significant weight, adding that among the past winners, she had been the "worst we ever had".

Mr Trump was responding to Hillary Clinton's claim that he called Ms Machado "Miss Piggy", though her rival repeatedly challenged her over where she had heard that remark.

The centrepiece of Mr Trump's case against Mrs Clinton was that the former senator and secretary of state is little more than a career politician who has squandered opportunities to address the domestic and international problems she is now pledging to tackle as president.

"She's got experience," he said, "but it's bad experience."

Mrs Clinton came armed with a wealth of detailed attack lines. She named an architect she said built a clubhouse for Mr Trump who says he was not fully paid, and quoted comments her rival had made about Iraq and about nuclear weapons.

When Mr Trump made a crack about Mrs Clinton taking time off the campaign trail to prepare for the debate, she turned it into a validation of her readiness for the White House.

"I think Donald just criticised me for preparing for this debate," Mrs Clinton said.

"And, yes, I did. And you know what else I prepared for? I prepared to be president. And I think that's a good thing."

The candidates sparred over trade, taxes and how to bring well-paid jobs back to the United States.

Mrs Clinton said her Republican rival was promoting a "Trumped-up" version of trickle-down economics - a philosophy focused on tax cuts for the wealthy. She called for increasing the federal minimum wage, spending more on infrastructure projects and guaranteeing equal pay for women.

Read more: The Midge - Some of the choicest cuts from the first live television debate between Hillary Clinton and Donald Trump

Mr Trump panned policies that he said have led to American jobs being moved overseas, in part because of international trade agreements which Mrs Clinton has supported.

He pushed her aggressively on her past support for the Trans-Pacific Partnership trade pact while she was serving in the Obama administration. She has since said she opposes the sweeping deal in its final form.

Mr Trump repeatedly insisted that he opposed the Iraq War before the 2003 US invasion, despite recorded evidence to the contrary. Presented with his earlier comments during the debate, Mr Trump responded: "I said very lightly, I don't know, maybe, who knows."

The Republican also appeared to contradict himself on how he might use nuclear weapons if he is elected president. He first said he "would not do first strike", but then said he could not "take anything off the table".

Mrs Clinton said Mr Trump was too easily provoked to serve as commander in chief and could be quickly drawn into a war involving nuclear weapons.

Illegal immigration and Mr Trump's promises of a Mexican border wall were not part of the conversation. And while Mrs Clinton took some questions on her private email server, she was not grilled about her family's foundation, Bill Clinton's past infidelities or voter doubts about her trustworthiness.