LANHAM (AFP) - US President Barack Obama hit the road Wednesday to prolong the impact of his State of the Union promise to act to cut the gap between the rich and poor.

Obama appeared at a Costco wholesale store in suburban Maryland to push his plan to raise the minimum wage from US$7.25 (S$9.25) to US$10.10 (S$12.90) an hour.

"The economy's been growing for four years now. Corporate profits, stock prices have all soared, but wages and incomes or ordinary people haven't gone up in over a decade," Mr Obama said.

Polls show that a majority of Americans support the idea of raising the minimum wage but the plan remains unlikely to pass Congress because Republicans oppose it, fearing it could hamper small business and jobs growth.

"Americans overwhelmingly agree, nobody who works full time should ever have to raise a family in poverty," Mr Obama said. "That's why I firmly believe that it's time to give America a raise."

Mr Obama is traveling to four states over two days to drive home his message in Tuesday's State of the Union address that upward mobility in America has slowed due to income inequality and that if Congress will not act, he will use his executive powers to do so.

Mr Obama vowed a "year of action" on Tuesday night to lift up workers, improve education and clean the environment. "America does not stand still - and neither will I," Obama said, talking past the lawmakers gathered in the House of Representatives directly to millions of television viewers.

But Republicans branded Obama's speech as tarnished by bad ideas, and blamed his policies for leaving America with an unemployment rate of 6.7 per cent after his first five years in office. "It as the same tired boilerplate we hear year after year," Republican Senate minority leader Mitch McConnell said.

"That's distressing news for our country. It's especially disheartening for the middle class." Obama's subtext on Tuesday was reviving a presidency that seems to be racing towards early lame duck status after a disastrous 2013.

He also needs to shield allied lawmakers from being pulled down by his relative unpopularity - he has a 43-per cent approval rating - and Democrats are in peril of losing the Senate in mid-term elections.

The president's reputation was sullied by the disastrous rollout of his signature health care law, a government shutdown drama and perceived missteps abroad last year.