WASHINGTON - US President Barack Obama is cutting into Republican challenger Mitt Romney's lead among likely voters nationally following the second and third presidential debates, the latest Gallup daily tracking poll showed on Wednesday.

The poll found Romney now leads over Obama by 50 percent to 47 percent among likely voters, the closest result since Gallup launched its tracking survey on likely voters on Oct 14.

The latest poll was based on a rolling seven-day average through Oct 23, the first one with polling data completely after the second presidential debate on Oct 16 in Hempstead, New York State, yet only one day of reaction to the final debate on Oct 22 in Boca Raton, Florida.

The previous Gallup polls on likely voters found that Romney maintained lead over Obama by between 5 and 7 points.

The latest poll also showed that Obama regained the marginal lead over Romney among registered voters, by 48 percent to 47 percent. The result is also the first time Obama led among registered voters in the Gallup poll since Oct 14.

Republican presidential nominee Mitt Romney (L) and US President Barack Obama shake hands at the conclusion of the final US presidential debate in Boca Raton, Florida, in this Oct 22, 2012 file photo. [Photo/Agencies]