WASHINGTON — Republicans have won enough seats to control the US House, completing the party's sweep into power and securing their hold on the US government alongside President-elect Donald Trump as he made a triumphant return to the White House and met with US President Joe Biden.

A House Republican victory in Arizona, alongside a win in slow-counting California earlier on Wednesday, gave the GOP the 218 House victories that make up the majority. Republicans earlier gained control of the Senate from Democrats.

With hard-fought yet thin majorities, Republican leaders are envisioning a mandate to upend the federal government and swiftly implement Trump's vision for the country.

Trump has promised to carry out the country's largest-ever deportation operation, extend tax breaks, seize control of the federal government's most powerful tools and reshape the US economy. The GOP election victories ensure that Congress will be onboard for that agenda, and Democrats will be almost powerless to check it.

Also on Wednesday, Trump chose Representative Matt Gaetz of Florida to serve as his attorney general, bypassing more experienced options in favor of a loyalist whom Trump has tasked with dramatically overhauling the Justice Department.

Trump also announced that he had tapped Senator Marco Rubio of Florida as his nominee for secretary of state. And he selected Tulsi Gabbard, a former Democratic member of Congress and presidential candidate, to serve as his director of national intelligence.

The choices continued a pattern of Trump stocking his team with those he believed he could trust to execute his agenda. Gaetz's selection, in particular, was seen as a shock. The Florida lawmaker was not among the more established attorneys who had been mentioned as contenders for the job.

Trump made a triumphant return to the White House on Wednesday, where Biden offered a show of civility to him.

The US president and president-elect shook hands in front of a roaring fire in the Oval Office.

"Welcome back," Biden, 81, said as he congratulated the 78-year-old Trump, the man he has repeatedly branded a danger to democracy, and pledged a smooth transfer of power.

Biden, who dropped out of the election in July but saw his successor Kamala Harris lose to Trump last week, said he would do "everything we can to make sure you're accommodated".

"Politics is tough, and in many cases it's not a very nice world. It is a nice world today and I appreciate it very much," said Trump.

Agencies Via Xinhua