Democratic candidate Kamala Harris and Republican candidate Donald Trump are contesting to win the White House.
The first election results in the US presidential election are gradually coming in, as polls in most states close and vote counting begins.
US media have projected wins for Trump so far in 24 states, including Texas, Florida, Missouri, Louisiana, Ohio, Kentucky and West Virginia.
Harris has so far captured 13 states including California, Delaware, Maryland, Massachusetts, Vermont and New York.
So far, that gives Harris 205 electoral votes and Trump 246.
The magic number to win the US presidency is 270.
Over 80 million people out of 161 million registered voters have cast their ballots so far.
A final outcome may not be known for several days if the results are as close as the polls suggest.
The two candidates wrapped up their campaigns on Monday night as they focused on swing states to sway undecided voters.
Observers expect the hotly contested race for the White House to come down to a number of key battleground states.
In the meantime, while much attention was on the race for the White House on Tuesday, American voters will also determine who will control both chambers of Congress.
All 435 seats in the House of Representatives and 34 seats in the Senate are up for grabs. Republicans currently hold a majority in the House, while Democrats control the Senate, both by slim margins.