OHIO (Reuters) - US President Barack Obama called people to "choose hope" as he made the case for electing Democrat Hillary Clinton as his successor in the White House.

At a rally in the battle ground state of Ohio, Mr Obama said Republican Donald Trump, "is uniquely unqualified to be president. He is temperamentally unfit".

He said Mrs Clinton, who served as Secretary of State under Obama, was a "good and decent person, who knows what she is doing and will be an outstanding president".

Opinion polls show Mrs Clinton's lead has narrowed slightly since early last week but it is too early to say if the email controversy is hurting her.

Mrs Clinton led businessman Trump in the latest Reuters/Ipsos poll of likely voters on Monday, by 44 per cent to 39 per cent. She is hoping to be the first woman elected to the White House.