Negative views of U.S. President Barack Obama have hit an all-time high in a new public opinion poll.

The ABC News/Washington Post poll puts the president's “unfavorable” rating at 49 percent, while 48 percent view him favorably.

President Obama has acknowledged his pursuit of re-election next year is not guaranteed.

“We're going to have to fight for it. It's not a slam-dunk.”

But the same poll shows Mr. Obama is viewed more positively than former House of Representatives Speaker Newt Gingrich, the current frontrunner for the Republican presidential nomination in the 2012 race.

Gingrich's unfavorable rating is 48 percent, but his favorable rating is 13 points lower than the president's at 35 percent.

In other polls this week, Gingrich still holds a significant lead in the fight for the Republican nomination. A Wall Street Journal/NBC News survey of likely Republican voters puts him 17 points ahead of former Massachusetts Governor Mitt Romney.

The latest figures come less than three weeks before the Iowa caucuses –the first voting in the nomination battle.