WASHINGTON, Oct. 27 (Xinhua) -- Despite falling behind in fundraising, former U.S. Vice President Joe Biden on Sunday expressed confidence in his presidential campaign.

"I know I'm the frontrunner," the Democratic presidential contender said in an interview with CBS News. "We're on a course to do extremely well. I'm not worried about being able to fund this campaign."

Biden raised 15.2 million U.S. dollars in the third quarter of this year, his campaign announced earlier this month.

In comparison, his fellow top-tier 2020 Democratic candidates, Senators Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts, took in 25.3 million dollars and 24.7 million dollars, respectively.

Unlike the campaigns of either Sanders or Warren, the Biden campaign has dropped its opposition to the formation of a super PAC, an independent political action committee that can raise unlimited sums from corporations, unions, and big donors.

Biden, 76, served as U.S. vice president from 2009 to 2017 to the nation's first African American president, Barack Obama.

According to a RealClearPolitics average of recent polls, he is currently leading Warren and Sanders by 5.4 points and 9.9 points, respectively.