Christians across the US are praying as the nation decides whether to reelect Barack Obama or put Republican rival Mitt Romney in the White House instead.
Prayer vigils and worship gatherings are being held at Lafayette Park across from the White House throughout the day until midnight.
Prayers will be said for a president who honours God and religious freedom, as well as human rights and justice for all.
The polls opened today after a tightly run race costing more than $2bn (£1.3bn).
The BBC reports that Obama and Romney were neck-and-neck in the last few days.
Final polls by Washington Post/ABC and Reuters/IPSOS showed Obama with a two to three point lead over Romney.
Christian development agency Tearfund said the next president would have a significant impact on communities in developing countries.
"Many of the issues on which Tearfund advocates are hugely influenced by the position and actions taken by the US government," the agency said.
"For example, our campaign to get a global deal on climate change needs the USA to support strong action.
"Too often, a lack of this has blocked progress, but leadership from the next president could help bring progress."
Tearfund is asking Christians to pray for the next president to "draw upon God for strength and wisdom" and "realise the importance of tackling climate change".
Both candidates spent the last day on the campaign trail addressing huge rallies.
"We know what the future requires, but we also know it's not going to be easy," Obama said at a rally in Madison, Wisconsin.
"Back in 2008 we talked about it. I know everybody sometimes romanticizes the last campaign - the posters and all the ... good feeling.
"But I said back then, when I'm talking about change, I'm not just talking about presidents or political parties, I'm talking about changing how our politics works."
Romney said in Lynchburg, Virginia: "If [Obama] were to get reelected, he would not be able to work with people in Congress.
"And I say that because he hasn't been able to. He has ignored them, he's attacked them, he's blamed them. And, by the way, if he can't work with Congress, think what happens the next time the debt ceiling comes up.
"The president was right when he said the other day that he can't change Washington from the inside. We're gonna give him a chance to try and change it from the outside."
Christians pray as US heads to the polls
Published 06 November 2012