US President Donald Trump speaks at a campaign rally at Hickory Regional Airport in Hickory, North Carolina, on Nov 1, 2020. (CHRIS CARLSON / AP)

OPA-LOCKA/WILMINGTON/HICKORY/PHILADELPHIA - US President Donald Trump will hunt for support in four battleground states on Monday while Democratic rival Joe Biden focuses on Pennsylvania and Ohio during the final day of campaigning in their long, bitter race for the White House.

The Republican Trump trails Biden in national opinion polls ahead of Tuesday's Election Day. But the race is seen as close in enough swing states that Trump could still piece together the 270 votes needed to prevail in the state-by-state Electoral College that determines the winner.

US President Trump will hold rallies on Monday in North Carolina, Pennsylvania, Wisconsin and two in Michigan. He won those states in 2016 against Democrat Hillary Clinton, but polls show rival Joe Biden is threatening to recapture them for Democrats

Trump, aiming to avoid becoming the first incumbent president to lose re-election since fellow Republican George H.W. Bush in 1992, will hold rallies on Monday in North Carolina, Pennsylvania, Wisconsin and two in Michigan.

He won those states in 2016 against Democrat Hillary Clinton, but polls show Biden is threatening to recapture them for Democrats.

Trump will wrap up his campaign in Grand Rapids, Michigan, the same place he concluded his 2016 presidential run with a post-midnight rally on Election Day.

Biden, running mate Kamala Harris and their spouses will spend most of Monday in Pennsylvania, splitting up to hit all four corners of a state that has become vital to the former vice-president's hopes.

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Joe Biden will rally union members and members of the African-American community in the Pittsburgh area before being joined for an evening drive-in rally in Pittsburgh by singer Lady Gaga.

Biden also will make a detour to bordering Ohio, spending time on his final campaign day in a state that was once considered a lock for Trump, who won it in 2016, but where polls now show a close contest.

Biden has wrapped up the campaign on the offensive, traveling almost exclusively to states that Trump won in 2016 and criticizing the president's response to the coronavirus pandemic, which has dominated the late stages of the race.

US Democratic presidential candidate and former vice-president Joe Biden speaks at a "Souls to the Polls" drive-in rally at Sharon Baptist Church in Philadelphia, on Nov 1, 2020. (ANDREW HARNIK / AP)

Biden accuses Trump of giving up on fighting the pandemic, which has killed more than 230,000 Americans and cost millions of jobs. Polls show Americans trust Biden more than Trump to fight the virus.

During a frantic five-state swing on Sunday, Trump claimed he had momentum. He promised an economic revival and imminent delivery of a vaccine to fight the pandemic. Anthony Fauci, the top US infectious diseases expert, has said the first doses of an effective coronavirus vaccine will likely become available to some high-risk Americans in late December or early January.

A 'terrible thing'

Trump again questioned the integrity of the US election, saying a vote count that stretched past Election Day would be a "terrible thing" and suggesting his lawyers might get involved. 

ALSO READ: Trump warns of vote count delays in US presidential election

Nearly 60 million mail-in ballots have been cast, which could take days or weeks to be counted in some states - meaning a winner might not be declared in the hours after polls close on Tuesday night

Americans have already cast nearly 60 million mail-in ballots that could take days or weeks to be counted in some states - meaning a winner might not be declared in the hours after polls close on Tuesday night.

"I don’t think it’s fair that we have to wait for a long period of time after the election," Trump told reporters. Some states, including Pennsylvania, do not start processing mail-in votes until Election Day, slowing the process.

Trump has repeatedly said without evidence that mail-in votes are prone to fraud, although election experts say that is rare in US elections. Mail voting is a long-standing feature of American elections, and about one in four ballots was cast that way in 2016.

Democrats have pushed mail-in voting as a safe way to cast a ballot in the coronavirus pandemic, while Trump and Republicans are counting on a big Election Day in-person turnout.

"We’re going in the night of - as soon as the election is over - we’re going in with our lawyers," Trump told reporters without offering further explanation.

Trump denied an Axios report that he has told confidants he will declare victory on Tuesday night if it looks like he is ahead, even if the Electoral College outcome is unclear.

"The president's not going to steal this election," Biden told reporters when asked about the Axios report.

Supporters of Democratic presidential candidate and former vice-president Joe Biden listen as Biden speaks at a rally at Franklin Delano Roosevelt Park,  in Philadelphia, on Nov 1, 2020. (ANDREW HARNIK / AP)

Trump on Sunday held rallies in Michigan, Iowa, North Carolina and Georgia, and at midnight, a late one in Florida.

At Opa-Locka airport in the Miami area, a "Fire Fauci" chant broke out when Trump defended his handling of coronavirus.

Fauci, a highly respected member of his coronavirus task force, has been increasingly critical of Trump's handling of the virus.

In response to the "Fire Fauci" chant, Trump said: "Don't tell anybody, but let me wait until a little bit after the election."

Democratic challenger Joe Biden is ahead 51 percent to 43 percent nationally in the latest Reuters/Ipsos poll, taken from Oct 27 to 29. But the race remains a toss-up in Florida, North Carolina and Arizona, Reuters/Ipsos polls showed, as President Donald Trump trails by 7 percentage points in Pennsylvania and 10 points in Michigan and Wisconsin

Biden, the former vice president, made several appearances in closely contested Pennsylvania, the state where he was born and one that is crucial to his quest for the White House.

"There is nothing he can do to stop this nation from voting," Biden told a drive-in rally in a parking lot outside a Philadelphia church, where supporters honked their car horns in approval.

"He knows that if you get to have your say, he doesn't stand a chance," Biden said.

Trump, buffeted by snow flurries in Washington, Michigan, a town north of Detroit, wore his trademark red cap emblazoned with the words "Make America Great Again" as he promised a boisterous crowd he would lead a recovery from the pandemic, which has killed more than 230,000 Americans and hammered the economy.

"I'm delivering the great American comeback, and we're not having any lockdowns," Trump promised.

'Never had anything like this'

Biden criticized Trump for encouraging his supporters after they harassed a Biden campaign bus in Texas. A caravan of vehicles bearing Trump campaign flags surrounded the bus carrying campaign staff on a highway on Friday, forcing the campaign to cancel two events.

"We've never had anything like this. At least we've never had a president who thinks it's a good thing," Biden told reporters.

Supporters listen as US President Donald Trump (not in frame) speaks at a campaign rally at Hickory Regional Airport in Hickory, North Carolina, on Nov 1, 2020. (CHRIS CARLSON / AP)

Trump on Saturday retweeted a video of the incident and wrote: "I LOVE TEXAS!" In Michigan, he asked supporters if they had seen videos of "our people" with the bus. 

"It was Trump Trump Trump and the American flag,” Trump said.

The FBI said on Sunday it had opened an inquiry into the Texas incident. The president later criticized the investigation, tweeting: "In my opinion, these patriots did nothing wrong."

A record-setting 93.2 million early votes have been cast either in-person or by mail, according to the US Elections Project, representing about 40 percent of eligible voters

Biden is ahead 51 percent to 43 percent nationally in the latest Reuters/Ipsos poll, taken Oct 27-29. The race remains a toss-up in Florida, North Carolina and Arizona, Reuters/Ipsos polls showed, as Trump trails by 7 percentage points in Pennsylvania and 10 points in Michigan and Wisconsin.

READ MORE: Trump casts ballot in US presidential election

A federal judge in Texas will consider on Monday whether Houston officials should throw out about 127,000 votes already cast at drive-through voting sites in the Democratic-leaning area. A Republican state legislator and others accuse Harris County Clerk Chris Hollins, a Democrat, of exceeding his constitutional authority by allowing drive-through voting as an alternative during the coronavirus pandemic.

Former president Barack Obama, who Biden served as vice-president for eight years, will hold a get-out-the-vote rally in Atlanta, Georgia, on Monday before closing out the campaign in the evening with a rally in Miami.