A spokeswoman for US First Lady Melania Trump has described comments by her husband's ex-wife Ivana as "attention seeking and self-serving noise".
Ivana Trump told ABC's Good Morning America she was "basically first Trump wife, I'm first lady".
She said she had a direct line to the White House but did not want to "cause any kind of jealousy".
The first Mrs Trump is promoting her book Raising Trump, to be released on Tuesday.
She was married to Donald Trump in 1977 but they divorced in the 1990s over his affair with his second wife-to-be Marla Maples.
Ivana and Donald had three children - Donald Jr, Ivanka and Eric Trump.
Ivana Trump told GMA she spoke to her former husband about once a fortnight.
"I have the direct number to White House, but I no [sic] really want to call him there because Melania is there," she said.
"I don't want to cause any kind of jealousy or something like that because I'm basically first Trump wife. I'm first lady, OK?"
Melania Trump responded with a barbed statement through her spokeswoman Stephanie Grisham.
"Mrs Trump has made the White House a home for [their son] Barron and The President," it read.
"She loves living in Washington, DC and is honoured by her role as First Lady of the United States. She plans to use her title and role to help children, not sell books.
"There is clearly no substance to this statement from an ex. Unfortunately only attention seeking and self-serving noise."
The exchange is thought to be the only public row between a US first lady and a president's former wife.
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