A former U.S. ambassador to Canada said that Americans are "not convinced" that President Joe Biden is the best candidate to prevent Donald Trump from returning to the White House.

In a statement posted on social media, Bruce Heyman said that Democrats should now consider alternative candidates for the 2024 presidential race.

Heyman said, "While I have great respect for President Biden and acknowledge his significant achievements, recent events have raised concerns about his ability to run an effective campaign for another term."

Heyman served as the U.S. ambassador to Canada from 2014 to 2017, during President Barack Obama's administration. He was sworn in by then-Vice President Biden.

Heyman's statement was published just before Biden took the stage at a long-awaited solo press conference marking the conclusion of the NATO summit in Washington. This was Biden's first appearance since his shaky performance in the presidential debate just two weeks earlier.

Facing the media, Biden reaffirmed his intention to run for a second term in the Oval Office "to finish the job I started," despite increasing calls for him to drop his reelection bid.

During that press conference, Biden made an attention-grabbing slip when he mistakenly referred to Vice President Kamala Harris as "President Trump’s vice president."

Responding to a question from Reuters about his confidence in Harris, Biden said, "I would not have chosen President Trump’s vice president to be vice president if she were not qualified to be president."

This mix-up came just hours after a NATO event where Biden mistakenly referred to Ukrainian President Volodymyr Zelensky as Russian President Vladimir Putin before correcting himself.

Heyman is not the only Democrat suggesting that Biden may not be fit to lead the United States for another four years.

Earlier this week, Hollywood actor and major Democratic Party donor George Clooney publicly joined the chorus of voices urging Biden to withdraw from the presidential race. More than ten Democratic lawmakers have called on the president to step aside.

Many of these Democrats suggested that Harris could be the party's nominee instead of Biden. Reports from The New York Times indicate that Biden's campaign team is conducting polls to see how Harris would perform against Trump.

Heyman stated that, although Harris "deserves respect," the party should avoid naming her as the presidential candidate "without a fair and robust selection process."

"The Democratic Party boasts a wealth of talented individuals who can lead us into the future," he said. "I propose a series of meetings, debates, and interviews to showcase these candidates, culminating in a convention in Chicago to select our nominee."

The Democratic National Convention is scheduled to take place from August 19 to 22 in Chicago. That is where the party will officially nominate its presidential candidate.

Heyman said that "given the significant stakes of this election," he will support the Democratic nominee, regardless of who it is.

He added, "However, we owe it to the American people to present the strongest possible candidate to lead us forward and protect our democracy."