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US First Lady Melania Trump accused her husband's first wife Ivana of making "attention-seeking and self-serving noise" Monday, after the former Mrs Trump jokingly referred to herself as the first lady while trying to sell her memoirs.

In an interview with ABC News to promote her new book ─ "Raising Trump" ─ the 68-year-old Ivana Trump attempted a little joke when describing her longstanding relationship with the 45th US president.

"I have the direct number to White House but I don't really want to call him there because Melania is there, and I don't really want to cause any kind of jealousy or something like that because I'm basically first Trump wife, OK? I'm first lady, OK?" she told ABC, with a laugh.

Melania Trump, 47 and normally very reserved, was not amused.

"Mrs. Trump has made the White House a home for Barron and the president," said a tersely worded statement from her spokeswoman Stephanie Grisham, published by CNN. Barron is the Trumps' young son.

"She loves living in Washington, DC, and is honored by her role as First Lady of the United States."

"She plans to use her title and role to help children, not sell books," Grisham said.

She added: "There is clearly no substance to this statement from an ex. This is unfortunately only attention-seeking and self-serving noise."

Ivana Trump is the mother of Trump's three eldest children: Donald Jr, Ivanka and Eric.

The former real estate magnate has two other children: Tiffany, with his second wife, Marla Maples, and 11-year-old Barron ─ who lives with his parents at the White House.

Ivana, a Czech-born former model, skier and businesswoman, married Trump in 1979. The couple were a fixture on the New York celebrity circuit before divorcing in a blaze of scandal in 1992.

Trump went on to marry Maples, with whom he had been having an affair, but they divorced six years later. Melania is Trump's third wife.

Ivana is perhaps best known for coining Trump's nickname "The Donald."