Joe Biden faces a tough re-election battle this November, but for one day at least The Force was with him.

Legendary "Star Wars" actor Mark Hamill made a surprise appearance in the White House briefing room on Friday after meeting the US president.

Hamill, 72, who played the powerful Jedi knight Luke Skywalker in the film series and is a vocal Biden supporter, took the podium wearing a pair of the president's trademark aviator sunglasses.

"I called him 'Mr President,' he said 'You can call me Joe.' And I said, 'Can I call you Joe-bi Wan Kenobi?' He liked that," quipped Hamill.

He was referring to "Star Wars" character Obi-Wan Kenobi, portrayed by Alec Guinness in the original 1977 film, who teaches Skywalker to discover his powers as he battles the dark side of The Force and the sinister Darth Vader.

Hamill described Democrat Biden, 81 -- who is set for an almost-as-epic battle with Republican predecessor Donald Trump in November's US election -- as "the most legislatively successful president in my lifetime."

The president had shown him photos during a meeting in the Oval Office, he added.

Taking a couple of questions from reporters -- although "no Star Wars questions please" -- the actor said he'd visited the White House under Democratic presidents Jimmy Carter and Barack Obama but "this one was really extra special."

The visit came on the eve of the so-called "May the Fourth" day, when "Star Wars" fans celebrate in a riff on the movie's catchphrase "May the Force be with you."

The White House regularly brings guests into press briefings but they are usually in support of a cause or policy.

South Korean K-pop sensations BTS visited in 2022 to highlight the issue of anti-Asian racism, while US actor Matthew McConaughey took the podium later the same year to urge "gun responsibility" following a massacre at an elementary school in his hometown of Uvalde, Texas.

White House Press Secretary Karine Jean-Pierre said Hamill was "someone who is... very much invested in the direction of this country."