DEMOCRATS vowed to use their resounding midterm victory to rein in President Donald Trump, setting up two years of possible deadlock in Washington, as Trump spent his first post-election appearance showing off his under-construction White House ballroom.

A wave of anger over Trump's policies, particularly the US-Iran war's role in pushing the cost of living higher, helped Democrats take the Senate, where they flipped seats in deeply Republican states for a majority of at least 54-44. Democrats also gained at least 30 seats in the House of Representatives.

It will be the first time that Trump, a Republican who also held the White House from 2017 to 2021, has had to contend with Democrats controlling both chambers of Congress.