Ivanka Trump stepped out as a potent surrogate for her father on Thursday, promising he would be a compassionate leader who would fight for women's rights and affordable childcare.

The 34-year-old businesswoman and mother of three, a loyal fixture on her dad's campaign trail, introduced the 70-year-old mogul as he accepted the Republican nomination for president that few imagined ever possible.

"My father not only has the strength and ability necessary to be the next president, but also the kindness and compassion that will enable him to be the leader that this country needs," said the elegant blonde.

For those disturbed by Trump's inflammatory comments about women, Muslims and immigrants, Ivanka presents a quandary: how can a woman whose public image is beyond reproach support him so lovingly?

The answer, apparently, is that America does not know the man as she does. Or as she diplomatically put it: "It is possible to be famous and yet not really well known."

Trump often gushes about Ivanka, her intelligence and business acumen, and her siblings acknowledge that she is the apple of her father's eye.

Yet she treads a careful line, supporting her father but equally careful never to say anything controversial, as she maintains a carefully curated public image as businesswoman and entrepreneur.

On Thursday she spoke to women, independents and young people, who resonated particularly strongly with defeated Democratic presidential candidate, Bernie Sanders, and referred to crippling college debt.

Millennial vote

"Like many of my fellow Millennials, I do not consider myself categorically Democratic or Republican," she said. "This is the moment and Donald Trump is the person to make America great again."

He was the single-most qualified person to lead the economy, and would "call on the best and brightest, both sides of the aisle," she said.

Trump, who polls as low as 34 percent among women, hired women on construction sites before it was commonplace, has more female than male executives and would introduce equal pay, she said.

"Women are paid equally and when a woman becomes a mother she is supported, not shut out," she said of life at The Trump Organization where she is a vice president of acquisitions and development.

"He will focus on making quality childcare affordable and accessible for all," she added, in comments that could have been lifted straight from the mouth of Trump's Democratic rival Hillary Clinton.

"American families need relief... He will fight for equal pay for equal work and I will fight for this too."

Ivanka's Instagram account is a heady mix of adorable pictures of her photogenic children, tips for working mothers and pictures of herself modeling elegant dresses from her affordable high-street range.

But behind the scenes, she is a force to be reckoned with. She reportedly urged her father to adopt a more presidential style and took exception to ugly nicknames he gave opponents.

Child of divorce

With her brothers Donald and Eric, she is thought to have been instrumental in persuading her father to pick conservative Indiana Governor Mike Pence as vice president in a bid to unite the party.

Born in 1981, she is the second child of Trump and his first wife, the Czech-born Ivana, whose marriage exploded in tabloid scandal and ended in divorce when she was 10 years old.

Privately educated at Chapin and Choate, some of the East Coast's most exclusive schools, she followed her father to the Wharton School at the University of Pennsylvania, graduating with a degree in economics.

Much has been made by the Trump children of the value of hard work that their parents instilled in them, and how they spent summers working rather than jetting off to the French Riviera with friends.

While the offspring of New York's super rich can be seen in and out of rehab, or struggling to hold down jobs, the Trump adult children are seemingly happily married and assets to his global corporation.

In addition to working for her father, Ivanka founded her eponymous fashion line, the Ivanka Trump Collection.

Married to multi-millionaire real estate developer and publisher Jared Kushner, for whom she converted to Judaism, the couple are fixtures on the society circuit but also known to like the quiet life at home.

AFP contributed to this report