Miami (AFP) - Hillary Clinton took to the stage with Jennifer Lopez in Miami late Saturday when the music superstar performed a free concert in the rain to encourage early voting in the battleground state of Florida.

The 47-year-old actress, singer and dancer whose toned physique appeared to defy gravity, powered through some of her greatest hits, including "Let's Get Loud" and "On the Floor" before an exuberant crowd who cheered and danced as rain drenched the outdoor amphitheater.

Clinton arrived for the last segment of the gig, after Lopez's ex-husband, Marc Anthony, had already performed. She enveloped Lopez in a bear hug, before thanking the former couple for their support.

The concert capped a day of campaigning in Florida for the Democrat nominee after America's top cop, FBI Director James Comey renewed his probe of her emails and her lead over Donald Trump narrowed.

Clinton lashed out at her Republican rival, accusing him of stoking fear, disgracing American democracy and insulting "one group of Americans after another, 10 days before the November 8 ballot.

Trump fired up his raucous supporters on Saturday with a vow that "justice can at last be delivered" with regard to Clinton's emails -- despite the FBI not putting any timeline on the new inquiry.

"Are we going to let Donald Trump get away with that? You're right. We're not," she said. "No matter what they throw at us, we don't back down. Not now. Not ever," the Democrat said.

"We just heard Jennifer perform Let's Get Loud, well I say let's get loud at the voting booth," the former secretary of state said.

"Don't wait another day to vote and lets get loud by knocking on doors, making calls, take out your phones," she said.

"Because if we turn out, we win!" she said to more cheers.

Although the rain came down heavily, the crowd seemed pretty pumped up as Lopez closed out with "On the Floor" and ticker tape paper dropped from the sky at the Bayfront Park Amphitheater.

On Saturday, the latest poll of polls by tracker site RealClearPolitics put Clinton 3.9 percentage points ahead of Trump nationwide, down from a lead of 7.1 points just 10 days previously.