US vice presidential candidate John Edwards has vowed that the Democratic party would "fight for every vote" after refusing to concede defeat in the key state of Ohio, where the result remains deadlocked.
"It's been a long night. But we've waited four years for this victory. We can wait one more night," Mr Edwards told a rally in the centre of Boston, the hometown of Democratic presidential contender Mr John Kerry.
"Tonight, John and I are so proud of all of you who are here with us and all of you across the country who have stood with us in this campaign. John Kerry and I made a promise to the American people that in this election every vote would count, and every vote would be counted.
The Democrats have refused to concede defeat in Ohio while two television networks have said President George W. Bush has won there, which would take him to verge of victory in the election.
For Mr Kerry to win Ohio, he must look to a yet-to-be calculated number of uncounted votes and hope he can win enough to overcome President Bush 's lead in the state.
Mr Bush led Mr Kerry by about 135,000 votes this morning but the big turnout has delayed a final count of crucial ballots with at least 54 counties still having some uncounted absentee votes.
In addition, an agency survey of election boards found about 140,000 provisional ballots in Ohio, cast by people whose names don't show up on regular poll lists. Secretary of State Kenneth Blackwell estimated the number could be as high as 175,000.
Mr Kerry could win if he did extremely well among provisional voters, but it would mean taking more than the 48.5 percent of regularly cast ballots he finished the night with.
Under Ohio law, the counting of provisional ballots begins 10 days after the election.
With all precincts reporting, unofficial results found Mr Bush had 2,794,346 votes, or 51 percent, while Mr Kerry had 2,658,125, or 48.5 percent.
Agencies