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Melania Trump 's legal battle with journalist Michael Wolff is getting uglier ... and Wolff says he can't wait to ask Melania and President Donald Trump about Jeffrey Epstein under oath.

Here's the deal ... Wolff filed a lawsuit Tuesday against the First Lady, claiming she threatened to sue him over public statements he's made linking her to the notorious pedophile Epstein. Gallery Launch Gallery Getty

We reached out to the Office of the First Lady of the United States ... and they told us, "First Lady Melania Trump is proud to continue standing up to those who spread malicious and defamatory falsehoods as they desperately try to get undeserved attention and money from their unlawful conduct." Getty

In response, Wolff told us he's never been

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