US President Joe Biden, buoyed by midterm elections in which his fellow Democrats fared better than expected, has said that Election Day was good for democracy but the results showed that Americans remained frustrated, reports Agence France Presse.

"It was a good day, I think, for democracy," Mr Biden said at the White House.

"While the press and the pundits were predicting a giant red wave it didn't happen," said Mr Biden, who had framed the race as a clash between defenders of democracy and the "extremist" camp of Donald Trump.

"Our democracy has been tested in recent years but with their votes the American people have spoken and proven once again that democracy is who we are," Biden said.

Mr Biden said while not all the results were yet known, he would continue to "work across the aisle" with Republicans regardless of the final election results.

With a majority of yesterday's races now called, Republicans made modest gains but Democrats performed better than expected, as control of the Senate hinged on three races that remained too close to call.

Control may hinge on a run off election in the southern state of Georgia on 6 December if neither candidate crosses the 50% threshold.

While in Arizona, Nevada and Wisconsin, counting the remaining votes for Senate could take days.

Republicans seemed on track to reclaim the House for the first time since 2018, but the midterms delivered a mixed bag for former president Donald Trump, who was widely expected to announce another White House run next week.

"Never underestimate how much Team Biden is underestimated," White House chief of staff Ronald Klain tweeted.

Mr Trump had been teasing a 2024 run and airing unsubstantiated allegations of Election Day fraud in recent days.

Speaking this evening he said that while in certain ways the election was somewhat disappointing, from his my personal standpoint it was "a very big victory".

While the night saw wins by more than 100 Republicans embracing Mr Trump's "Big Lie" that President Biden stole the 2020 election, several high-profile, election-denying acolytes of the former president came up short.

Aiming to deliver a rebuke of Mr Biden's presidency, against a backdrop of sky-high inflation and bitter culture wars, Republicans needed one extra seat to wrest control of the evenly divided Senate.

But by early this morning the only seat to change party hands went to the Democrats, with John Fetterman, a burly champion of progressive economic policies, triumphing in Pennsylvania.

In the House, early results suggested Republicans were on track for a majority, but only by a handful of seats, a far cry from their predictions.

Top Republican Kevin McCarthy, who hopes to be the lower chamber's next speaker, struck an upbeat note, telling supporters in the early hours: "It is clear that we are going to take the House back."

But Senator Lindsey Graham, a top Trump ally, bluntly conceded to NBC that the election is "definitely not a Republican wave, that's for darn sure."

The president's party has traditionally lost seats in midterm elections, and with Mr Biden's ratings stuck in the low 40s and Republicans pounding him over inflation and crime, pundits had predicted a drubbing.

That would have raised tough questions on whether America's oldest-ever commander in chief, who turns 80 this month, should run again.

Instead, President Biden stands to emerge in much better shape than either of his Democratic predecessors, Barack Obama or Bill Clinton, who both took a hammering at the midterms.

Control of the Senate hinges on four key races, as Democrats need two more wins to successfully hold the chamber, while Republicans need three to flip it.