Former President Donald J. Trump has secretly spoken with President Vladimir V. Putin of Russia as many as seven times since leaving office, even as he was pressuring Republicans to block military aid to Ukraine to fight Russian invaders, according to a new book by the journalist Bob Woodward.

The book, titled “War” and scheduled to be published next week, describes a scene in early 2024 at Mar-a-Lago, Mr. Trump’s estate in Florida, when the former president ordered an aide out of his office so he could conduct a phone call with Mr. Putin. The unidentified aide said the two may have spoken a half-dozen other times as well since Mr. Trump left the White House.

The book also reports that Mr. Trump, while still in office early during the Covid-19 pandemic in 2020, secretly sent Mr. Putin what were then rare tests for the virus for the Russian’s personal use. Mr. Putin, who has been described as particularly anxious about being infected at the time, urged Mr. Trump to not publicly reveal the gesture because it could damage the American president politically. “I don’t want you to tell anybody because people will get mad at you, not me,” Mr. Putin reportedly told him.

The disclosures raise new questions about Mr. Trump’s relationship with Mr. Putin just weeks before an election that will determine whether the former president will reclaim the White House. A copy of the book was obtained by The New York Times. The Washington Post, where Mr. Woodward has worked for more than half a century, and CNN, where he often appears as a commentator, also reported on the book on Tuesday.

Mr. Trump’s campaign dismissed Mr. Woodward’s book by assailing the author with typically personal insults — “a total sleazebag,” “slow, lethargic, incompetent and overall a boring person with no personality” — without addressing any of the specifics reported in it.

“None of these made-up stories by Bob Woodward are true and are the work of a truly demented and deranged man who suffers from a debilitating case of Trump Derangement Syndrome,” Steven Cheung, the campaign communications director, said in the statement. Mr. Cheung said Mr. Trump did not give Mr. Woodward access for the book and noted that the former president was suing the author over a previous book.

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