Joe Biden's team have accused Donald Trump of 'trying to strip Americans of their voice' and warned 'our legal teams are ready'.
The comments came in response to the president's earlier address to the nation from the East Room of the White House.
'Frankly we did win this election,' Trump said. 'We want all voting to stop. We don't want them to find any ballots at four in the morning and add them to the list.'
Biden campaign manager Jen O'Malley Dillon said in a statement: 'If the president makes good on his threat to go to court to try to prevent the proper tabulation of votes, we have legal teams standing by ready to deploy to resist that effort.
'It was outrageous because it is a naked effort to take away the democratic rights of American citizens.
'It was unprecedented because never before in our history has a president of the United States sought to strip Americans of their voice in a national election.'
The outcome of the presidential race may not be known until the end of the week as several critical battleground states need more time to count the high number of mail-in ballots in the election.
Officials in Wisconsin, Pennsylvania and Michigan warned results are not coming in their states on Tuesday night, adding to the tension that has come with a presidential election like no other.
Wisconsin and Michigan may have results on Wednesday morning but Pennsylvania's results probably won't be known until Friday.
Compounding the problem are lawsuits expected over disputed ballots, which could drag out the results of the election even longer. Republicans have made it clear they will sue when and where they see necessary.
But Trump effectively declared victory in the deadlocked election at 2.30am Wednesday morning, calling Tuesday's election a 'fraud on the American people' and saying that he was going to the Supreme Court to demand that 'all voting stop.'
Continuing her statement O'Malley Dillon added: 'Having encouraged Republican efforts in multiple states to prevent the legal counting of these ballots before Election Day, now Donald Trump is saying these ballots can't be counted after Election Day either.
'And it was incorrect because it will not happen. The counting will not stop.
'It will continue until every duly cast vote is counted.
'Because that is what our laws — the laws that protect every Americans' constitutional right to vote — require.
'We repeat what the Vice President said tonight: Donald Trump does not decide the outcome of this election.
'Joe Biden does not decide the outcome of this election. The American people decide the outcome of this election.
'And the democratic process must and will continue until its conclusion.'
The delayed results were caused by state laws that limited when mail-in ballots could be counted, record voter turnout, and the hundreds of thousands of mail-in ballots that were received.
Also outstanding is Georgia after a water pipe burst at a center in Fulton County, where Atlanta is located, delayed counting ballots in the highly-Democratic area.
The candidates took different approaches to the delay with Biden urging patience and Trump falsely claiming Democrats were trying to steal the election.
More than 92 million Americans requested mail-in ballots, according to the Election Project. Many states expanded that voting option because of the coronavirus.
Most of those ballots were requested by Democratic voters - President Trump urged his supporters to go to the polls on Election Day - meaning a great deal of the uncounted ballots are expected to break for Biden.
This article has been adapted from its original source.
© Associated Newspapers Ltd.