US Democrats win Nevada, maintain Senate majority

American President Joe Biden's Democrats retained control of the US upper house on Saturday, as incumbent Catherine Cortez Masto won Nevada to give the party the 50 seats it needs for an effective Senate majority.

Senator Catherine Cortez Masto celebrates with Nevada Governor Steve Sisolak in Las Vegas. AP - Gregory Bull

The Nevada win clinches Democratic control in the Senate as Vice President Kamala Harris can cast the tie-breaking vote if the upper chamber is evenly split 50-50.

The Senate seat for Georgia remains unfilled. There will be a run-off there on 6 December, but the result can only strengthen the position of the Democrats.

Maintaining control of the Senate means Biden and the Democrats will retain leverage in legislative debates, particularly on domestic and foreign spending policy.

The result in the lower chamber House of Representatives still hangs in the balance, and while Republicans are slightly favored to take control, it will be with a far smaller majority than they had envisaged going into last Tuesday's election.

Trump plays the fraud card

Speaking minutes after the Nevada projections were announced, Senate Majority Leader Chuck Schumer said the result showed Americans "soundly rejected the anti-democratic, authoritarian, nasty and divisive direction the MAGA Republicans wanted to take our country," referring to former president Donald Trump's "Make America Great Again" movement.

Trump was omnipresent on the campaign trail, putting his thumb on key Republican primaries and holding rallies nationwide, during which he repeated his baseless claims of fraud in the 2020 race.

Several of Trump's hand-picked candidates underperformed and the Republicans' poor showing overall was a damaging political blow.

Trump is set to declare his 2024 White House bid on Tuesday, an announcement he had planned as a triumphant follow-on to an expected crushing election victory by the party he still dominates.

Chuck Schumer stressed that the Democrats' win would ensure a "firewall" against moves by Republicans in Congress to further curtail abortion rights -- a key issue in the mid-terms.

The Senator for New York also urged the two parties to "try to come together" to end "divisive negativity".