Detroit, Michigan - Joe Biden again rejected any notion he would quit the presidential race and tried to turn the spotlight on Donald Trump as he took his crisis-hit reelection bid back on the campaign trail Friday.

But as he addressed a lively rally in Detroit, Michigan, the drumbeat of Democrats urging the 81-year-old Biden to step aside kept getting louder following a disastrous debate performance against Trump.

"There's been a lot of speculation lately. What's Joe Biden going to do, is he going to stay in the race, is he going to drop out?" Biden told supporters in, to chants of "Don't you quit!"

"Here's my answer: I am running and we're going to win! I'm not going to change that," Biden said.

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But opposition continued to grow in spite of Biden's defiance.

Nineteen Democratic lawmakers have now called on him to bow out of the race due to concerns over his health and mental acuity in the wake of the June 27 debate debacle.

A series of gaffes at Thursday's high-stakes press conference on the sidelines of the NATO summit in Washington DC, including referring to Vice President Kamala Harris as "Vice President Trump" and mixing up Ukrainian President Volodymyr Zelensky with Russia's Vladimir Putin, kept the focus on his fitness to serve.

At the Detroit rally, Biden tried to brush off the blunders by taking a leaf out of the Trumpian book.

In scenes more reminiscent of his rival's rallies, reporters in Detroit were booed after Biden targeted them and said they were "hammering me because I sometimes confuse names."

Biden urged the media to focus on Trump's "lies" and on "Project 2025," a blueprint for power by hard-line conservatives that Democrats have said the former president would implement, but which the 78-year-old denies involvement in.

"Americans want a president, not a dictator," Biden said. Referring to Trump's comment that he would only be a dictator on "day one" of his presidency, Biden said he would let that happen "over my dead body."

Earlier, Biden said "I promise you I am OK" as he addressed supporters at a diner.

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Biden, who blamed jet lag and illness for his stumbling debate performance, will keep up a relentless travel schedule in coming days as he seeks to allay concerns over his stamina and sharpness.

Next week, he heads to Texas and Nevada to reach out to his vital Black and Latino voters, and will give another major network interview on Monday, to NBC.

"The president understands that there's still some anxiety," Biden campaign communications director Michael Tyler told reporters traveling to Michigan with the president aboard Air Force One.

"That's why he's laser focused on demonstrating that he is the best person to take on Donald Trump," he said.

Tyler played down the verbal slip-ups, saying: "Joe Biden has been making gaffes for 40 years, he made a couple of last night, he probably will continue to do so."