Christians in the US are praying God's will be done as Americans prepare to cast their votes in an election that has been nail-bitingly close to the end. 

Polling shows that Democratic hopeful Kamala Harris and Republican candidate Donald Trump are neck and neck.

Harris dubbed it "one of the closest races in history" in her final campaign speech at a star-studded rally in Philadelphia. In an earlier rally in Pittsburgh she said she wanted to be a "president for all Americans".

Trump wrapped up his campaign in Michigan late on Monday night. He used his final day of campaigning to attack immigration and hurl insults at his political opponents. He also alluded to recent assassination attempts.

"Many people say that God saved me in order to save America," Trump told the rally. "It's a beautiful expression and I think it might be true."

More than 81 million Americans have already voted early and millions more will cast their votes throughout Tuesday. 

Evangelical leader Franklin Graham has spent the last few weeks urging people to pray and get out and vote.

"Today we are on the eve of the most important election in the history of our nation. Join me in praying that God's will be done," he told his 10 million Facebook followers last night.

Earlier he wrote, "Our country is in trouble, and there's so much at stake. The election is just a couple of days away and may be the most important election in the history of the U.S. Pray that God will protect us from the evil that is before us." 

Harvest pastor Greg Laurie said, "As we look forward to this year's elections for our country's leaders, we should all be praying." 

He told Americans to trust in God with the nation's future no matter who wins the election.

"Presidential elections are big events. Billions of dollars are poured into campaigns that run for two years or more. Candidates become fixtures on our television screens and social media feeds. And we start to invest ourselves in the process. We develop a rooting interest. Sometimes, that means rooting for a candidate; sometimes, it means rooting against one," he said. 

"The more of a stake we have in the outcome of an election, the more likely we are to be anxious about it. The doom-and-gloom predictions about what will happen 'if X becomes president' feed that anxiety. Jesus' words in Matthew 6:33–34 are a reality check: 'Seek the Kingdom of God above all else, and live righteously, and he will give you everything you need. So don't worry about tomorrow, for tomorrow will bring its own worries. Today's trouble is enough for today' (NLT).

"The things that may change following an election are insignificant compared to the things that absolutely will not change. God still sees the future. He knows the outcome of every decision. His hand is on the steering wheel. He cares about you. And He will always be with you." 

John McLaughlin, a pollster for Trump in 2016 and 2020, told "The Rosenberg Report" on TBN that the evangelical vote would be critical in this election. 

"We do see in the polls that we're running over 70 per cent of support with Evangelical voters — that's strong," he said.

"But I'll tell you what, there are Evangelical voters who may not vote because some of them think Trump's got it in the bag, he's going to win ... Some of them think that their votes don't really count. Well, in this race, your votes do count."