Kim Kardashian has finally pledged her support to husband Kanye West after he announced his plans to run for U.S. president.

The reality star, 39, took to Twitter on Friday, after days of silence following her husband's news that he plans to take on incumbent Donald Trump and Democratic nominee Joe Biden, to retweet a video of the rapper explaining to Americans how to register to vote.

Kim's delayed public support comes amid claims people close to the star are "very concerned" about Kanye, who appears to be "in the middle of a serious bipolar episode".

In the video, Kanye said: "Hey what's up everybody, I'm here at the County Clerk's office. I wanted to show you how I just registered to vote."

He continued: "There's a lot of people who think they can't vote they're a convicted felon but they can actually ask for their rights back."

Kanye announced his plan to run on Sunday, adding Kim and Tesla boss Elon Musk would be his chief advisers. And while she didn't elaborate on her involvement in her husband's campaign, the tech billionaire has shared some doubts he's having about his new role.

"We may have more differences of opinion than I anticipated," he answered when a Twitter user asked Musk how he could still support Kanye after reading a recent interview he'd done with Forbes.

According to editors at TMZ, a source has claimed the Gold Digger hitmaker is in the throes of a serious bipolar episode and those close to him are concerned it has impacted his decision-making.