Donald Trump has said if Hillary Clinton is elected US president she "will start World War Three".

The Republican presidential candidate said America should focus on defeating so-called Islamic State rather than Syria.

"She has no plan for Syria. You'll end up with World War Three. She doesn't know what she's doing," he told Reuters news agency.

"Just like with Libya, just like everything else she has done...she's incompetent," he added.

Mr Trump claimed if he had party unity he would not lose the election to Democrat candidate Mrs Clinton.

"If the Republicans could come back into the tent, we would not lose this election," he said.

At a rally in Florida on Tuesday - two weeks before the US election - Mr Trump repeated his vow to "repeal and replace" the outgoing US president's Obamacare if he gets into office.

Mrs Clinton has said she wants to keep the best of the programme, but would make improvements.

US rapper Jay Z has said he will hold a free concert in Cleveland in support of Mrs Clinton.

Cleveland was also the site of a free get-out-to-vote concert Jay Z held in support of Barack Obama just days before he was elected president in 2008.