Donald Trump has declared a congressman "would be dead by June" in news that was not publicly known.

"Tell them the story," Trump said with a laugh.

Johnson then began to explain the situation.

"Congressman Neal Dunn of Florida has had some real health challenges," Johnson said.

"It was very serious and had a pretty grim diagnosis."

As Johnson was speaking, Trump interjected: "He would be dead by June".

"Okay, that wasn't public," Johnson said.

The crowd in the room audibly groaned at the revelation but Trump remained smiling before laughing and patting Johnson on the back.

Johnson then discussed how Trump recommended doctors for Dunn for an operation.

The president then described a conversation he had with Johnson about how Dunn's death would impact legislating in the House.

"Number one, it was bad because I liked him. Number two, it was bad because I needed his vote," Trump said.

Dunn recently had surgery and has had a "new lease on life", Johnson said.

Republicans have just a two-vote majority in the House of Representatives.

Dunn had previously announced he would not be running for re-election in November but denied reports he was quitting before his term was over.

The congressman, himself a doctor, has not spoken publicly since Trump's revelation.

Democrats are highly favoured to win control of the House in the midterm elections.

Meanwhile, the president also announced that his chief-of-staff Susie Wiles had been diagnosed with breast cancer.

Wiles, perhaps Trump's most powerful advisor, will continue working at the White House as she receives treatment.

"She has a fantastic medical team, and her prognosis is excellent! During the treatment period, she will be spending virtually full time at the White House, which makes me, as President, very happy!" Trump said on Truth Social.

"Her Strength and her Commitment to continue doing the job she loves, and does so well, while undergoing treatment, tells you everything you need to know about her."

Wiles is considered one of the most powerful people in the USA despite her low-profile.

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