ST. PAUL, Minn. - Republican Sen. Norm Coleman's lead over Democratic challenger Al Franken grew slightly yesterday as a special Minnesota board began refereeing more than a thousand disputed ballots in a process expected to last several days.

Coleman led Franken by 264 votes, up from 188, after the five-member state Canvassing Board spent about five hours squinting at piles of ballots trying to figure out exactly what voters intended. The board focused almost entirely on challenges from the Franken campaign that were mostly brought to try to keep a Coleman vote off the board.

It is the nation's last unresolved Senate race.

The board hoped to make it through about 1,400 challenges by week's end. It went through only 161 the first day, but attorneys for both campaigns said they would probably withdraw more challenges based on the board's early decisions. If that happens, Secretary of State Mark Ritchie said, the board could still finish by Friday.

Coleman added 98 votes to his total and Franken picked up 22; 41 more went to neither man. In coming days board members will take up a greater portion of Coleman's challenges, and if they dismiss them at a similar rate, Franken is likely to regain lost ground.

A recount of the Nov. 4 election was automatic because Coleman led Franken by just 215 votes out of almost 2.9 million cast. A statewide recount reduced the gap to 188, a number dwarfed by the mountain of disputed ballots.

Besides the challenged ballots, legal wrangling continues over about 1,600 wrongly rejected absentee ballots that the Canvassing Board asked counties to sort and count. Coleman's campaign petitioned the state Supreme Court seeking to halt that process, saying the board failed to set uniform standards for it. A hearing is set for today.