Six hours of contract talks Thursday night only seemed to create more distance between Anoka-Hennepin teachers and the state's largest school district.

With an April 17 strike-authorization vote on the horizon, the two sides met for the 17th time to try to forge a two-year contract that's 10 months overdue. In a rare move, three school board members attended the talks, which started at 5 p.m. and continued until 11.

Each side criticized the other, using terms like "taking a step backward" and "moving the goalposts."

Anoka-Hennepin is the last large Minnesota district still at the negotiating table. Minneapolis, St. Paul, Osseo, Rosemount-Apple Valley-Eagan and South Washington have all reached agreements with teachers.

Pay and health issues are sticking points in the Anoka-Hennepin talks.

School board Chairman Tom Heidemann said Friday that he thought the two sides were close to a deal walking into Thursday's meeting, but that a new union demand changed the tenor of the talks.

The district has offered raises and $1,000 one-time bonuses. Senior teachers, who make up 60 percent of the faculty, would receive raises of 1.5 percent the first year and 2 percent the second year. Less experienced teachers would receive 0 percent the first year and 1.5 percent the second.

On Thursday, representatives of Anoka Hennepin Education Minnesota, the union representing 2,700 teachers, said they wanted the $1,000 to be in the form of two $500 raises vs. one-time bonuses.

"This was a huge step backward to our goal of reaching a settlement last night," Heidemann said Friday.

The district was to spend $2.7 million of its reserve funds to pay those one-time bonuses and could not afford to make them permanent, he said.

Union President Julie Blaha said that "for these two years it doesn't change the cost. The question is are they willing to make a long-term commitment to teachers?"

Blaha also said that senior teachers accepted a pay freeze during the last two rounds of contracts.

"We really believe we have done our share when were times were difficult. Now it's time to get back on track," she said.

The two sides also could not agree on benefits, including changes to health care. In another pay-related issue, the district wants to add a 12th year in the teachers' step schedule, which the union opposes.

The district, which had declined to talk publicly about specifics for months, shared more details about talks for the first time Friday.

"Right now the community has only heard one point of view that would be heavily tailored to the union's point of view," Heidemann said. "We need to start communicating with the community about what the facts are."

Heidemann said the district and the teachers are now about $5.5 million apart.

Still, both sides said they're willing to sit down again, although no new mediation date has been set yet.

"Nobody wants to close a door here. We have to keep working," Blaha said.

Anoka-Hennepin salaries range from $37,000 for new teachers to $80,000 for those with more than two decades of experience and advanced degrees. The average Anoka-Hennepin teacher salary in 2012-13 was $62,300, the eighth-highest in the state. The St. Paul School District topped the list at more than $67,000 while neighboring Centennial was around $56,000.

The teachers union set the April 17 strike authorization vote after talks deteriorated earlier this month. If the vote passed, it would authorize their leaders to call a strike.