Washington D.C. - President Donald Trump and his rival, Democratic nominee Joe Biden, hit the road on Sunday, two days before the election, matching their ground game with a blitz of social media activity.

Both candidates pressed home their core messages, as polls appeared to tighten but still showed Biden with a lead over Trump, including in key swing states, though the outcome is far from certain.

Trump, who was the first out with supporters at a rally, warned that Biden would handle the coronavirus pandemic by imposing endless lockdowns and damaging the economy. He indicated Biden would mimic measures being implemented abroad.

"Europe imposed draconian lockdowns and cases were surging and deaths were surging, but think of it, draconian," Trump told supporters in Michigan, a northern state he needs to win.

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"Now, they have to do it all over again. What the hell are they doing? I think I'll go over and explain it to them," Trump said, pledging to never support shutting down again.

Despite the president's threats, most restrictions in the US are imposed by governors and local officials, not the federal government.

The US is hitting new record daily caseloads, with deaths and hospitalizations also climbing. More than 230,000 people have died in the country so far.

Public health officials are warning of a difficult winter ahead and there is growing concern the Trump administration has stopped trying to contain the outbreak, simply banking on drug companies developing therapeutics and vaccines soon.

Biden has run much of his campaign on a message of actively getting the virus under control, while rebuilding an economy which was shattered in March and ending the "chaos" of the Trump era.

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"It's time for Donald Trump to pack his bags and go home," Biden said at a rally in Philadelphia. "It's time to bring some life back into this nation. We're done, we're tired of the tweets, the anger, the hate, the failure, the irresponsibility."

Biden attacked Trump for his handling of Covid-19, saying the White House has been "almost criminal" as he noted blacks and other minority groups have disproportionately suffered in the pandemic, and vowed to deliver "racial justice."

The former vice president spent the morning at church in Delaware, his home state, before heading to neighboring Pennsylvania, which is becoming the key battleground.

Both candidates are presenting this election as the most important in their lifetimes, saying the very character of the country is on the ballot.

Biden has been far more cautious regarding the coronavirus pandemic, including holding fewer and smaller rallies, while the president is trying to pack outdoor arenas as much as possible, regularly saying he enjoys the greater enthusiasm.

Biden also promised to get a dog in the White House, a dig at the incumbent who, in a rarity for a president, does not have a pet.

Trump will be in at least five states on Sunday, while Biden will focus only on Pennsylvania, an eastern swing state which both candidates see as a must-win.

Biden got a boost from Barack Obama, the former president, who helped him campaign in Michigan on Saturday. The northern state narrowly voted for Trump in 2016, but Biden leads in polls. Obama is also due in Georgia on Monday, as Democrats seek inroads in the Deep South.

There are also growing worries about potential for violence on or after election day, with shops in some areas boarding up their storefronts and police gearing up for confrontations.

One incident getting attention took place at the weekend in Texas, where a convoy of cars driven by Trump supporters appears to have intimidated a Biden campaign bus on the highway, endangering the occupants of the bus, by driving overly close to it.

Trump issued a tweet late on Saturday, showing video of the trucks and cars ambushing and surrounding the bus, set to a pro-Republican rap song. "I LOVE TEXAS!" he wrote.

After reports that the FBI was looking into the incident he on Sunday tweeted that "these patriots did nothing wrong."