Republicans took control of the US House of Representatives in Washington on Wednesday.
The new Congress was sworn in two months after heavy losses were inflicted on President Barack Obama's Democrats mid-term elections in November.
The House of Representatives was called to order shortly after midday local time and Nancy Pelosi (Democrat, California) turned over the Speaker's gavel to John Boehner (Republican, Ohio) in an official exchange of power.
Ms Pelosi described the gavel as a "strong symbol of peaceful democracy".
The BBC reports the Republicans now control the House for the first time in more than four years. The Democrats have only a slim lead in the Senate.
Republicans say they will agree to lifting a limit of $US14.3 trillion on federal borrowing only in return for spending concessions.
Party leaders have vowed to slash federal spending by as much as $US100 billion.
Mr Boehner said Americans want a government that is honest, accountable and responsive to their needs. He warned of "hard work and tough decisions" ahead on the economy.
"No longer can we fall short. No longer can we kick the can down the road. The people voted to end business as usual, and today we begin carrying out their instructions," Mr Boehner said.
Healthcare repeal bill
An attempt will be made to repeal Mr Obama's reform to America's healthcare system next week.
The move is expected to pass in the House, but fail in the Senate.
Earlier on Wednesday Republican and Democratic leaders took part in a by a bipartisan prayer service at St Peter's Catholic Church in Washington.
On Thursday, the Republicans will have the US Constitution read aloud in the House chamber.
