Top U.S. government scientist Anthony Fauci said on Sunday that an advertisement aired by Donald Trump's campaign was edited to make him appear to endorse the president's handling of the coronavirus pandemic.

"In my nearly five decades of public service, I have never publicly endorsed any political candidate," said Fauci, the longtime director of the National Institute of Allergies and Infectious Diseases.

The 30-second campaign ad, released last week, refers to Trump's personal experience with the virus. "President Trump is recovering from the coronavirus and so is America," it says. "Together we rose to meet the challenge, protecting our seniors, getting them life-saving drugs in record time, sparing no expense.”

Then comes a brief clip of an interview with Fauci, in which he says, "I can't imagine that anybody could be doing more." 

Though no date is provided in the ad, the quote is from a Fox News interview with Fauci in March. During the interview, the top health expert praised the White House coronavirus task force's round-the-clock effort to respond to the pandemic. "We're talking about all hands on deck. I, as one of many people on a team, I'm not the only person," said Fauci at the time.

"I have been devoting almost full time on this. I'm down at the White House virtually every day with the task force. It's every single day. So I can't imagine that under any circumstances that anybody could be doing more."

On Sunday, Fauci said: "The comments attributed to me without my permission in the GOP campaign ad were taken out of context from a broad statement I made months ago about the efforts of federal public health officials."

In response to Fauci saying the ad took his words out of context, Trump campaign communications director Tim Murtaugh was quoted by CNN as saying that, "these are Dr. Fauci's own words. The video is from a nationally broadcast television interview in which Dr. Fauci was praising the work of the Trump Administration. The words spoken are accurate, and directly from Dr. Fauci's mouth."

As a leader of the White House task force on the coronavirus, Fauci has often had to walk a fine line in trying to clarify or correct the president's assertions about the disease or treatments and vaccines being developed against it.

Fauci has at times aroused Trump's anger, as shown when the president in April retweeted a message containing the hashtag #FireFauci, before publicly insisting he was doing a great job.

(With input from agencies)