U.S. President Joe Biden capped a half-century political career on Wednesday with a final Oval Office speech as he hopes to seal a legacy overshadowed by Democrats' failure to stop Donald Trump from returning to the White House.

Biden opened his speech with a familiar message — asking Americans to join together — but quickly warned about a dangerous concentration of wealth in the United States.

"Our system of separation of powers, checks and balances may not be perfect, but it has maintained our democracy for nearly 250 years, longer than any other nation in history that's ever tried such a bold experiment," Biden said.