US President Barack Obama's job approval rating has increased to 50 per cent, extending his lead over his top Republican challenger Mitt Romney, a latest national opinion poll said on Tuesday.
While Obama's approval rating climbed to 50 per cent, his disapproval rating dropped to 44 per cent in Gallup's Daily tracking poll on Obama's support among US voters.
Gallup said the 50 per cent approval mark is notable because all incumbent presidents since Dwight Eisenhower who were at or above 50 per cent approval at the time of the election were re-elected.
At the same time, Obama held a lead of 49-42 per cent over Romney, who is widely expected to secure his nomination soon after the Republican primaries in five states held Tuesday.
That marks a shift from last week, when Romney held an edge in Gallup tracking, the poll said.
Obama's job approval rating has typically been in the mid-40 per cent range for the last three months, it noted.
One possible reason for Obama's recent rise is the decline in gas prices.
Rising gas prices have often been associated with a decline in presidential approval ratings, Gallup said.