Republicans are "frustrated" with Donald Trump's last days before the election, according to a former top advisor to Barack Obama on Saturday.

As the vote draws closer, the former president is failing to remain on course, which is concerning his supporters, according to David Axelrod on CNN.

“A lot of Republicans are frustrated because Trump keeps getting off message and they would like him to be on the same message that his campaign is communicating on television in its advertising,” Axelrod said.

The vice president [is] talking about how unhinged and vengeful and so on Trump is. He is actually abetting her message in the final week, and that has to make Republicans uncomfortable.”

A separate report earlier Saturday claimed a senior adviser to Trump has got so frustrated with him veering off the message created for him — regarding issues such as immigration and the economy — that she called a meeting with him and demanded “this can’t go on.”

But Axelrod said the last few days had shown him unable to heed her.

“I am sure they would love him to stay tethered to the prompter a little bit more and deliver the message they think will help him win this election,” he said.

“But, he is not closing well. [Harris] is closing in a much more disciplined way. … She has been criticized for being too cautious, but being disciplined in the final 72 hours is really an advantage if you are on message.

“Being undisciplined can be very damaging.”