WASHINGTON - President Donald Trump on Thursday (Nov 5) sought to cast doubt on the legitimacy of the US election even as the counting of votes continued in key battleground states, alleging that results were being manufactured without substantiating his claims.

"If you count the legal votes, I easily win," he said in an address from the White House. "If you count the illegal votes, they can try to steal the election from us."

Mr Trump currently has the lead in the battleground states of Georgia and Pennsylvania, where counting is ongoing, but results released throughout the day have shown his lead dwindling as later-counted votes from urban centres and mail-in ballots favour Democratic candidate Joe Biden.

By Thursday night, Mr Trump's lead in Georgia stood at less than 2,000 - practically neck and neck with Mr Biden there, according to AP. In Pennsylvania , he is leading 26,000 votes or 0.4 point as votes continued to be counted. But Mr Biden's lead in Arizona also diminished to 46,300 or 1.6 points, as more results came in.

Shortly after Mr Trump's White House appearance, Mr Biden wrote on Twitter: "No one is going to take our democracy away from us."

Mr Biden had earlier called for patience, saying that every vote needed to be counted and that he was confident that the final count would show they had won.

In his address, Mr Trump complained about his lead in swing states being eroded as more votes were counted, and touted the Republican Party's achievements in House and Senate races, as well as a growth in support from minority voters.

"They're trying to rig an election, and we cannot let that happen," he said. "Our goal is to defend the integrity of the election. We'll not allow the corruption to steal the election."

Mr Trump has long criticised mail-in ballots, alleging that they are susceptible to fraud, although studies have shown otherwise. On Thursday he repeated the claims, saying: "It's really destroyed our system...it makes people corrupt even if they aren't by nature."

"They're finding ballots all of a sudden... It's amazing how the ballots are so one-sided," he added, referring to how mail-in ballots tend to lean Democrat.

His message came hours after Mr Biden spoke from his hometown of Wilmington, Delaware.

"Each ballot must be counted, and that's what we're going to see," Mr Biden said from his hometown of Wilmington, Delaware.

"Democracy is sometimes messy. It sometimes requires a little patience as well. But that patience has been rewarded now for more than 240 years with a system of governance that's been the envy of the world," he added.

The battleground states of Georgia, Pennsylvania and Nevada currently hold the key to the presidential election.

Mr Biden has 264 electoral votes, six away from the 270 needed to win the White House, including Arizona which some outlets have not called for the former vice-president.

Mr Trump is ahead in Georgia and Pennsylvania, but Mr Biden closed in on his lead in both states throughout the day as more votes were counted.

The Biden campaign said earlier that they expected him to come out ahead in Pennsylvania and that he could win Georgia, which was shaping out to be a true toss-up race.

Pennsylvania Secretary of State Kathy Boockvar said in the early afternoon that "we definitely could" know who won in Pennsylvania by the end of Thursday, adding that all of the ballots would be counted by Friday.

In Nevada, which has six electoral votes, Mr Biden holds a slim lead that expanded slightly on Thursday as more results were released. But counting there is not expected to conclude soon.

Mr Biden said that he and his running mate, California senator Kamala Harris, were confident that the final count would show they had won.

"We continue to feel very good about where things stand," he said. "So I ask everyone to stay calm. The process is working, the count is being completed, and we'll know very soon."

Mr Biden and Mrs Harris were briefed in the afternoon by a panel of experts on the coronavirus pandemic and the economic crisis.

"Cases are on the rise nationwide and we're nearing 240,000 deaths due to Covid, and our hearts go out to each and every family who has lost a loved one to this terrible disease," Mr Biden said in his remarks.

The Trump campaign has mounted a slew of legal challenges to stop vote counting or dispute the votes being counted in key states.

In Georgia, a judge threw out a Trump campaign lawsuit alleging that 53 ballots could have been received after the Nov 3 7pm deadline, writing that there was no evidence the votes had been accepted late.

In Michigan, which was called for Mr Biden on Wednesday afternoon, a judge also dismissed a challenge from the Trump campaign to halt absentee ballot counting for Republican observers to be granted "meaningful access" to the counting.

The count had been largely completed, said the judge.

In Pennsylvania, a judge ruled to allow Republican observers to watch the counting from six feet away rather than the original 20 feet away, which the Trump campaign had requested. Democrats appealed, arguing that the closer access was a stalling tactic.

As poll workers scrambled to tally ballots in Pennsylvania, supporters of both Mr Trump and Mr Biden held tense demonstrations at the main vote counting centre in Philadelphia, the state's largest city. Biden supporters want every vote counted, while Trump backers want votes that came in by mail after election day be ignored

Mr Trump had alleged, without proof, voter fraud in states he had lost in a series of tweets that were flagged by Twitter as misleading or disputed.

"All of the recent Biden claimed States will be legally challenged by us for Voter Fraud and State Election Fraud. Plenty of proof - just check out the Media. WE WILL WIN! America First!" he said. Twitter marked the tweet as disputed.

For live updates and results, follow our US election live coverage.