Washington DC - Independent US presidential candidate Robert F. Kennedy Jr. has scheduled a major speech for Friday amid mounting speculation that he could pull out of the election.

"Independent Presidential Candidate Robert F. Kennedy Jr. will address the nation live on Friday about the present historical moment and his path forward," he posted on his website on Wednesday.

The politician wants to speak in Phoenix, Arizona, where Republican candidate Donald Trump is also making a campaign appearance on Friday.

Kennedy's vice-presidential candidate Nicole Shanahan had recently brought into play a possible merger with the Trump campaign.

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ABC News reported that Kennedy was planning to withdraw from the election campaign. According to people familiar with the situation, he is leaning towards backing Trump but has not yet made a final decision on the matter.

Shanahan had explained in an interview that there were two options for Kennedy's team. Either he could stay in the race and risk Democrat Kamala Harris winning the presidential election on November 5, or else support Trump now.

Robert Kennedy, the nephew of former president John F. Kennedy, faces a very tough path to winning the presidential election. Current opinion polls give him an average of around 5% of the vote.

However, both the Democrats and the Republicans are looking at him with concern. The election is a neck-and-neck race between Trump and Harris.

Kennedy could take decisive votes from either major party. It currently looks as if his candidacy is more likely to hurt Trump – so a withdrawal by Kennedy would tend to be good news for the Republican.