Donald Trump has said he does not expect Joe Biden to end his bid to be re-elected president of the United States, suggesting he will stay in the race because of his ego.

In a telephone interview with Fox News host Sean Hannity on Monday night, the Republican candidate said that Biden “might very well stay in” the race despite mounting pressure to drop out due to concerns over his physical and mental fitness.

“He’s got an ego and he doesn’t want to quit,” Trump said. “He doesn’t want to do that. It just looks to me like that’s what he wants.”

Trump, the presumptive Republican nominee, said that the Democratic Party could do little to force Biden out of the race, apart from invoking a constitutional provision that enables the vice president and cabinet members to declare that the president is unable to discharge his duties.

“He has all the power, he has the delegates,” Trump said. “He doesn’t have to get out.”

Trump said that he expects Vice President Kamala Harris to be the Democratic nominee if Biden does choose to step aside.

“I think it will be her,” he said. “I think they are very concerned about the vote if it’s not her… They are gun shy, they don’t want to do it any other way.”

Trump’s comments came after Biden on Monday again slapped down calls for him to quit following his disastrous debate performance last month, insisting in a letter to Congressional Democrats that he is committed “to running this race to the end, and to beating Donald Trump”.

Six elected Democrats have so far publicly called on Biden to step aside since the debate, during which Biden stumbled over his words and appeared to lose his train of thought.

A number of other Democratic lawmakers have publicly raised concerns about Biden’s ability to beat Trump given his age and condition.

Biden has nonetheless so far managed to keep most of the Democratic top brass onside, with Senate Majority Leader Chuck Schumer and House Minority Leader Hakeem Jeffries on Monday reiterating their support for the president.

In his interview with Fox News, Trump also addressed last month’s debate for the first time, calling it a “strange evening”.

“I thought his voice was weak, I didn’t know exactly what was happening,” he said of Biden.