President Donald Trump joked in an interview with Bloomberg on Thursday that the White House press secretary, Sarah Huckabee Sanders, was "having a nervous breakdown" over his response to Sen. John McCain's death.

Sanders reportedly stared at him as he refused to answer whether he thought McCain would have been a better president than Barack Obama, who defeated McCain in the 2008 election.

Trump told Bloomberg he believes he properly honored McCain following his death.

President Donald Trump joked in an interview with Bloomberg on Thursday that the White House press secretary, Sarah Huckabee Sanders, was "having a nervous breakdown" as she stared at him when he refused to answer whether he thought Sen. John McCain, who died on Saturday, would have been a better president than Barack Obama.

McCain, the Republican presidential nominee in 2008, lost that election to Obama.

"I don't want to comment on it," Trump told Bloomberg. "I have a very strong opinion."

He added: "Maybe I'll give you that answer some day later."

Trump also insisted in the interview that he properly honored McCain after the longtime senator and Vietnam War veteran died from brain cancer.

The White House lowered its flag to half-staff immediately after McCain's death but raised it back to full staff Monday morning. After some blistering criticism from veterans groups, Trump ordered it back to half-staff later Monday.

US Flag Code requires the flag to be flown at half-staff "on the day of death and the following day" for a member of Congress. But US presidents have usually signed proclamations calling for flags to remain at half-staff until a prominent US official's interment.

Meghan McCain, the daughter of Sen. John McCain, with her father's casket on Wednesday. Reuters

On Thursday evening, as McCain's casket arrived for memorial services in Washington, DC, Trump headlined a rally in Indiana.

White House aides had considered the optics of such a move but decided to go through with it anyway, The New York Times reported Wednesday.

McCain and Trump feuded for years over public policy and other matters.

In 1999, Trump downplayed McCain's military service and suggested he was considered an American hero only because he was captured and held as a prisoner of war for five years in Vietnam.

Trump repeated those remarks during his 2016 campaign.

"We had our disagreements, and they were very strong disagreements," Trump told Bloomberg. "I disagreed with many of the things that I assume he believed in."

Trump also said he didn't think that he failed to unite the country around McCain's death.

"No, I don't think I did at all," Trump said. "I've done everything that they requested and no, I don't think I have at all."

He added of McCain: "I respect his service to the country."