WASHINGTON, United States (AFP) — A defiant US President Joe Biden insisted Thursday that he will run for another term and beat Republican rival Donald Trump during a press conference marred by verbal gaffes that threw a harsh new spotlight on his fitness.

In the presser at the end of the North Atlantic Treaty Organization (NATO) summit in Washington, the 81-year-old acknowledged the need to “allay fears” among Democrats but said he was determined not to step aside.

His bid to portray himself as in command was undermined by introducing Ukraine’s President Volodymyr Zelensky as his Russian foe Vladimir Putin earlier in the day, and then referring to Vice President Kamala Harris as “Vice President Trump” at the news conference.

Biden fielded a series of foreign and domestic policy questions with detailed if occasionally meandering answers and relatively few slip-ups, though he did mix up Europe and Asia.

With questions swirling about his ability to hold his own against autocratic leaders like Putin or China’s Xi Jinping, Biden said he was “ready to deal with them now and three years from now.”

Yet his relatively assured performance failed to stop the bleeding, with three more Democratic lawmakers calling for him to quit the race, bringing the total to 17.

Trump meanwhile mocked Biden over his gaffes during the press conference itself.

A poll released on Thursday showed more than half of Democrats say Biden should end his bid for a second term, and two-thirds of Americans believe he should quit the race.

Biden and Trump remain in a dead heat at 46 to 47 percent support among voters, respectively, according to the Washington Post-ABC News-Ipsos survey.