President Donald Trump called coronavirus expert Anthony Fauci a “disaster” on Monday, airing his frustration with the scientist during a call meant to reassure campaign staff he has a path to victory on Nov 3, despite trailing in opinion polls.

Trump and Fauci, a member of his coronavirus task force, have been at odds over how best to handle a pandemic that has killed more than 219,000 people in the United States and weakened the Republican president’s case for re-election.

Fauci, 79, who has served under Republican and Democratic presidents and is one of the most admired scientists in the United States, has urged that Covid-19 continue to be taken seriously. Trump has suggested the worst has passed...