US President Donald Trump says he intends to go to the Supreme Court after alleging ‘‘a major fraud on our nation’’ had been committed in the US election.

In a speech held at 2am in Washington, Mr Trump also proclaimed victory over Democratic challenger Joe Biden, despite incomplete results from battleground states that could determine the outcome of the race.

‘‘Frankly, we did win,’’ Mr Trump told supporters at the White House.

The President said he was in a celebratory mood with news from various states that he was expecting a ‘‘big win’’.

But he alleged fraud in what he said was an embarrassment for the voting process that would be tested in the Supreme Court.

Mr Trump said he wanted all voting to stop and no more votes found to count.

“This is a very sad moment,’’ Mr Trump said.

“We will win this and, as far I’m concerned, we already have.”

The President’s declarations came as the traditionally republican state of Arizona was called for Mr Biden, making the outcome of the election even more uncertain.

Arizona is a critical battleground state that Mr Trump won four years ago and represents a massive blow to the President’s chances of re-election.

Arizona, which has backed a Democratic presidential candidate only once in the last 72 years, is among the more than half a dozen states that will help determine which candidate gets the 270 electoral votes to capture the White House.

Election results from the battleground states of Pennsylvania, Wisconsin, Michigan and Georgia were also unclear.

Mr Trump asserted that he was “winning everything, and all of a sudden it was just called off”.

“Literally, we were just all set to get outside and just celebrate something that was so beautiful, so good, such a vote, such a success,” he said.

“Frankly, we did win this election,” Mr Trump said.

“We want the law to be used in a proper manner, so we’ll be going to the US Supreme Court. We want all voting to stop,” he added.

“We don’t want them to find any ballots at 4 o’clock in the morning and add them to the list. It’s a very sad moment.”

Leading Republicans expressed distress at Mr Trump’s claims.

Speaking on US ABC News, former New Jersey Governor and Trump adviser Chris Christie called the Mr Trump’s speech the wrong move – both strategically, and as president.

“It’s a bad strategic decision,” he said. “It’s a bad political decision.”

Former Republican senator Rick Santorum said he was “very distressed” by Mr Trump’s comments.

“Using the word fraud… I think is wrong,” he said on CNN.

Earlier, Mr Biden told a crowd in Delaware ‘‘We believe we’re on track to win this election’’.