Republicans on Wednesday took control of the US House of Representatives from Democrats, networks said, narrowly securing a legislative base to oppose President Joe Biden's agenda for the final two years of his term –- and leaving power in Congress split.

The slim Republican majority in the lower house of the US legislature was far smaller than the party had been banking on, and Republicans also failed to take control of the Senate in a historically weak performance in the November 8 midterm elections.

NBC and CNN projected the victory for Republicans with at least 218 seats in the 435-member House of Representatives -- the magic number needed to take control. This came a week after millions of Americans went to the polls for the midterms, which typically deliver a rejection of the party in the White House.

Biden congratulated top House Republican Kevin McCarthy "on Republicans winning the House majority" and added that he was "ready to work with House Republicans to deliver results for working families."

Last week's vote, he said, was "a strong rejection of election deniers, political violence and intimidation" and demonstrated "the strength and resilience of American democracy."

Tweeting soon after the projection was called, McCarthy said that "Americans are ready for a new direction, and House Republicans are ready to deliver."

The news came one day after former president Donald Trump -- who loomed large during the election cycle, and whose endorsement appears to have doomed some of his party's candidates -- announced a new run for the White House.

With inflation surging and Biden's popularity ratings cratering, Republicans had hoped to see a "red wave" wash over America, giving them control of both houses and hence an effective block over most of Biden's legislative plans.

But instead, Democratic voters -- galvanized by the Supreme Court's overturning of abortion rights and wary of Trump-endorsed candidates who openly rejected the result of the 2020 presidential election -- turned out in force.

And Republicans lost ground with candidates rejected by moderate voters as too extreme.