Washington, Oct. 20 : Democrat Barack Obama has expanded his national lead over Republican John McCain in the US presidential race to six percentage points, according to a new poll.

Obama now leads McCain 50 per cent to 44 per cent among likely US voters in the latest three-day tracking poll, up from Obama''s three-point advantage on Sunday, reports The Telegraph.

The results come after Obama was endorsed by Republican former Secretary of State Colin Powell.

It ends a string of three consecutive days when McCain had gained ground on the Illinois senator after their final debate on Wednesday. It was the first time in 14 days of the tracking poll that Obama has reached 50 per cent.

"Obama has really consolidated his base, and now has huge leads among young people, African-Americans and Hispanics," said pollster John Zogby.

"Reaching 50 percent puts him in winning territory," he added.

The poll, conducted by Reuters/C-SPAN/Zogby, has a margin of error of 2.9 percentage points.

Obama also increased his support among two key swing groups. His edge with independents rose from 8 points to 11 points, and his lead among women grew from six to eight points.

McCain narrowly trails Obama among men and leads by 13 points, 53 percent to 40 percent, among whites. (ANI)