Exuberant Republicans vowed on Wednesday to exercise their new power in Congress to roll back some of US President Barack Obama's key accomplishments, but a somber Obama said voters wanted both parties to work harder to find common ground.

"It's pretty clear the American people want a smaller, less costly and more accountable government," Republican John Boehner, in line to become the next House of Representatives speaker, told reporters. "Our pledge is to listen to the American people."

Voters, anxious about the economy and unhappy with Obama's leadership, punished Democrats in an election rout on Tuesday that gave House control to Republicans and weakened the Democratic majority in the Senate.

A chastened Obama called the result "a shellacking" and told a White House news conference the solutions demanded by frustrated Americans would be hard to find.

"I'm not suggesting this will be easy," he said. "The overwhelming message that I hear from the voters is that we want everybody to act responsibly in Washington, we want you to work harder to arrive at consensus."

Republicans picked up 60 House seats in the election, knocking Democratic Speaker Nancy Pelosi from power and putting Republicans in charge of House committees. It was the biggest shift in power since Democrats gained 75 House seats in 1948.

Boehner and Republican Senate leader Mitch McConnell said voters wanted them to roll back the signature initiatives passed by congressional Democrats in the last two years like healthcare and financial regulatory reforms.

But a divided government is more likely to fuel a legislative stalemate when the new Congress begins in January. Senate Democrats can block House initiatives, and Obama's weakened hand will still hold the veto pen.

Top Republicans showed little inclination to compromise.

"We're determined to stop the agenda Americans have rejected and to turn the ship around," McConnell said. "We'll work with the administration when they agree with the people and confront them when they don't."