Ivanka Trump takes her father's seat at world leaders' table during a G-20 meeting

HAMBURG — President Trump's daughter and adviser Ivanka Trump has an expansive portfolio in her father's administration. But on Saturday, she literally took his seat at the table at the Group of 20 summit.

The first daughter was spotted slipping into Trump's seat at a working session on "Partnership with Africa, Migration and Health," putting her shoulder to shoulder with British Prime Minister Theresa May. Russian President Vladimir Putin was sitting one seat down.

Trump's presence at the high-level table was somewhat unusual, given that government ministers or senior officials are typically the ones called to stand in for heads of state at such sessions. But she is both the president's daughter and an unpaid "assistant to the president" who focuses on issues of women's empowerment and workplace development, and she maintains broad influence in the administration.

She entered the session with her father but "briefly joined the main table when the President had to step out," a spokesperson for the first daughter said.

It isn't the first time Ivanka Trump has participated in high-level meetings at the summit. On Thursday night, she and her husband, Jared Kushner, another Trump adviser, joined the president at a bilateral meeting with German Chancellor Angela Merkel. Kushner also participated in Trump's bilateral meeting with Mexican President Enrique Peña Nieto on Friday.

Asked about Ivanka Trump's presence at the table on Saturday, Merkel did not weigh in on whether it was appropriate, but she said that the decisions about who sits at the table should be left to the American delegation.

"The delegations themselves decide, should the president not be present for a meeting, who will take the chair, and Ivanka Trump was part of the American delegation," Merkel said at a press conference. "It is very well known that she works at the White House and that she is engaged in certain initiatives."

Another U.S. official, Nikki Haley, the U.S. Ambassador to the United Nations, also defended Trump in an interview with CBS's "Face the Nation."

"She's got her certain issues that she focuses on, and when those things come up, then that's where she is and that's what she likes to focus on," Haley said, adding that Trump has sometimes sat in on meetings with her and the president. "I think she sees herself as part of a public servant family, and she doesn't want to waste this time by not putting forward some effort to try and help the world."

"And so, I think that's what she's doing is fighting for small businesses in our country, fighting for women entrepreneurs, fighting to make sure that we are not only being just good with the United States, but we're also internationally doing our part, whether it's poverty or famine or whether we see it's migration," Haley added. "And so those are the things I think that she's working on, and I think she's been very well accepted nationally and internationally."

Earlier on Saturday, Ivanka Trump and her father participated in a World Bank session on women's entrepreneurship, an issue that she has been particularly focused on.

In his remarks, Trump praised his daughter effusively for her work as a "forceful advocate" for female entrepreneurs: "I'm very proud of my daughter, Ivanka — always have been, from day one — I had to tell you that, from day one," Trump said. "She's always been great. A champion. She's a champion."

Ivanka Trump has taken up a slate of issues since taking a role in the West Wing, including workforce training, paid family leave and women's economic empowerment. But she has also weighed in on major disputes within her father's administration, including disagreeing with her father on his decision to leave the Paris climate accord.

Much has been made of the degree to which she disagrees with him on tone and substance. And on Saturday, Trump seemed to acknowledge that he often puts his daughter in a difficult position. "If she weren't my daughter, it would be so much easier for her," Trump said. "Might be the only bad thing she has going, if you want to know the truth."

She has defended the role she plays in her father's administration, saying that while she disagrees with him, she does not always air those disagreements in public.

"I would say not to conflate lack of public denouncement with silence," she told CBS in an interview in April. "I think there are multiple ways to have your voice heard.

"In some cases, it's through protest and it's through going on the nightly news and talking about or denouncing every issue on which you disagree with. Other times it is quietly and directly and candidly," she added. "So where I disagree with my father, he knows it, and I express myself with total candor."

The president and his older daughter also differ greatly in terms of temperament. Ivanka reportedly pleaded with her father to apologize after the disclosure of a 2005 tape from "Access Hollywood" in which he bragged about sexually assaulting women.

While she is known for her measured discipline, her father frequently lashes out at his perceived enemies on social media and in public. Most recently, he attacked Mika Brzezinski, calling the MSNBC host "crazy" and claiming that she was "bleeding badly" from her face after a cosmetic surgery operation.