President Joe Biden on Thursday mistakenly referred to Vice President Kamala Harris as "Vice President Trump" in the opening question of his highly-anticipated solo press conference in Washington.

"Look, I wouldn't have picked Vice President Trump to be vice president [if] I think she's not qualified to be president," Biden said, confusing his second-in-command with his November election opponent, former President Donald Trump.

A reporter pointed out Biden's mistake in the final question of the press conference, asking the president to comment on the blunder after Trump used it to mock him. Biden smiled to himself and replied, "Listen to him," before walking off stage.

Thursday's press conference was billed as the best opportunity for Biden to prove to Democrats that could handle tough questions and think on his feet in an unscripted environment.

Pressure for Biden to drop out of the 2024 race has escalated for weeks, following his disastrous debate performance against Trump on June 27 and his campaign's subsequent failure to assuage voters' concerns about his health.

It quickly became clear that Biden's hourlong press conference did not put Democrats' concerns to rest, however.

Four minutes after he walked off stage, Rep. Jim Himes of Connecticut, the top Democrat on the House Intelligence Committee, released a statement calling on Biden to exit the race.

Shortly afterwards, Rep. Scott Peters, D-Calif., did the same. "The stakes are high, and we are on a losing course," Peters said in a statement.

As he has throughout the week, Biden rigidly rejected any suggestion that he should or would drop out, insisting that there was no one more capable of beating Trump in November than he was.

Biden did, however, concede that he would consider exiting the race if his team came and told him there was "no way" he could win.

Despite coming in on a mission to rescue his teetering campaign, the president misspoke and appeared to lose his train of thought several times, as he fielded reporters' questions. Trump and his campaign posted several clips of Biden's gaffes on Truth Social.

In another memorable slip, Biden referred to his chief of staff as "my commander in chief" before catching his mistake.

He also sometimes delivered meandering responses, like a seven-minute answer to a question about China. As he gave it, he occasionally trailed off mid-sentence and tripped over his words.

"Some of our European friends are going to be curtailing their investment in Russia, I mean, excuse me, in China," the president said.

When he cited numbers, he repeatedly prefaced with a disclaimer that he might get the number wrong: "Don't hold me to the exact number."

Biden also often interrupted himself mid-sentence, diverting to unrelated topics as he worked to make his case for reelection: "There's so much we can do still. I'm determined to get it done. It's about freedom. By the way, I'll end this, well I'm not going to do that ... Haley has to come up too," he said before trailing off.

Earlier Thursday evening, Biden added salt to his political wounds at a scripted NATO event honoring Ukraine where he accidentally introduced Ukraine President Volodymyr Zelenskyy as "President Putin."

"And now I want to hand it over to the President of Ukraine, who has as much courage as he has determination. Ladies and gentlemen, President Putin," Biden said, before quickly correcting himself.

The last time Biden held a solo press conference was in November 2023 after his meeting with Chinese President Xi Jinping in California.

This time around, the president faced a new level of pressure with the future of his reelection campaign in the balance.

Each day since his June debate flop, new cracks have emerged in Biden's support from Democratic lawmakers, donors, fundraisers and strategists.

Hours before Biden's highly-anticipated press conference, one of his campaign officials told NBC News that the president needs to drop out: "He'll never recover from this."