US President Barack Obama has increasingly gained in his popularity rating and leading the odds against two leading potential Republican challengers in the 2012 presidential elections, latest opinion polls said.

"President Barack Obama's numbers are on the rise in two important indicators of his reelection chances, according to a new national survey," the CNN said as it released the results of the CNN/ORC International Poll.

The poll indicated Obama's margins have increased against five possible Republican presidential challengers in hypothetical general election matchups and his approval rating is up five points since mid-November.

According to the poll, Obama leads leading Republican candidate Mitt Romney 52 per cent - 45 per cent in a possible 2012 showdown.

Romney, who's making his second bid for the GOP nomination, held a 51 per cent - 47 per cent margin over the president in last month's survey, CNN said.

Obama also leads against other top Republican candidates, Newt Gingrich, Rick Perry, Ron Paul and Michele Bachmann.

"Bill Clinton and George W Bush - the last two presidents who won reelection had roughly this same amount of support in December of the year before the election, but so did Bush's father in December of 1991. He ended up losing in the general election," says CNN Polling director Keating Holland.

However, the White House said Obama is right now focused addressing key challenges facing the country.

"I will simply say that polls go up and down. We live in a very challenging political environment and, more importantly, in a continuingly challenging economic environment," White House Press Secretary, Jay Carney said.

"This President's focused on the challenging economic environment, and admittedly, in focusing on that, he has to content with the challenging political environment," the White House Press Secretary, Jay Carney said.

"But right now he is committed to working with Congress and doing the things he can do outside of Congress to grow the economy and help it create jobs.

"I think that in these last several months that focus has been pretty clear. He is going to continue that focus. And the impact that has on polls remains to be seen. But it is his primary focus as President," Carney told reporters at his daily news conference.