WASHINGTON (AFP) - White House hopeful Hillary Clinton traded vicious barbs with her Democratic rival Barack Obama on Friday as they rode guns blazing into the final weekend before Pennsylvania's key primaries. Their bitter standoff as they battle for the Democratic Party's ticket to stand in the November elections has turned increasingly nasty since they faced off Wednesday in a lacklustre debate. Obama has lashed out at the format of the debate on ABC television, after he was put on the defensive over his fiery former pastor, comments that some working Americans were "bitter" and his reluctance to wear a US flag lapel pin. But Hillary retorted Friday: "I've been through, what 23 of these debates? And as I recall I was asked some pretty tough questions in nearly every one of them. That goes with the territory. "We need a president who is going to be up there fighting every day for the American people and not complain about how much pressure there is and how hard the questions are," she sniped. Furious Obama campaign staff shot right back, accusing the former first lady of hypocrisy after she and her husband, former president Bill Clinton, both complained of media bias towards the Illinois senator in past months. "Considering the fact that Senator Hillary sat on stage at the last debate and complained to all America that she always gets the first question, her blatant hypocrisy here is stunning," said Obama spokesman Bill Burton. He accused Hillary of "talking about the same distractions and divisions that Washington is obsessed with" rather than debating the real issues. Ahead of Tuesday's pivotal vote in Pennsylvania, Obama has a slight advantage having won more states since the nominating contests kicked off in January. And though he holds more delegates, both are still short of the 2,025 delegates needed to secure the party's nomination. With Republican Party presumptive nominee John McCain already campaigning hard, there is a glaring need for closure in the Democratic contest, with national polls showing a tight race in the November vote. Both Democratic hopefuls were campaigning hard in Pennsylvania on Friday, where polls show Clinton holding a six-point lead. That would fall short of the blowout she needs to seriously dent Obama's lead in elected delegates, going into the next two primaries in Indiana and North Carolina on May 6. "Anything less than a double-digit victory could solidify the perception that Illinois Senator Barack Obama is the inevitable Democratic nominee, sparking a flow of superdelegates to his side," the Wall Street Journal said Friday. Nearly 800 superdelegates are the Democratic kingmakers and can vote for either candidate at the party's nominating convention in August, and about 250 have not yet announced who they would support. In her quest to become the country's first female president, Hillary is slightly ahead in the superdelegate tally over Obama, also bent on making history by being the first African-American elected to the Oval Office. A victory in Pennsylvania could win over more superdelegates for Clinton, although a poll published Friday in USA Today said dozens of uncommitted superdelegates would not see Tuesday's results as decisive in their choice. "Pennsylvania matters. But so do the other states that have voted or intend to vote over the next two months," Donna Brazile, a member of the Democratic National Convention, told the daily. But Oregon Secretary of State Bill Bradbury told the paper that Pennsylvania "could be the final call," adding that if Obama has a strong showing it could end doubts over his ability to appeal to white, working-class men. According to the latest tally by independent pollsters RealClearPolitics.com, Obama has a total of 1,647 delegates to Clinton's 1,507. There are 158 more up for grabs on a proportional basis in the Pennsylvania primaries.