WASHINGTON (AFP) - President Barack Obama has postponed a planned campaign event for Hillary Clinton in the pivotal swing state of Florida as powerful Hurricane Matthew barrels towards the Sunshine State, the White House said.

Obama had been due to appear near Miami on Wednesday (Oct 5), trying to help the Democratic nominee solidify her poll lead over Republican Donald Trump in a state that could well decide the outcome of November's election.

He was also scheduled to give a speech on health care in Tampa.

That event has also been cancelled.

"Due to the expected, or at least the potential impact of Hurricane Matthew here in the United States, President Obama has decided to postpone his travel to Florida," said White House press secretary Josh Earnest.

The Category Four storm is currently projected to graze the east coast of the United States, travelling up the coasts of Florida, South Carolina and North Carolina.