WARSAW, Poland — Unions representing Poland's public school teachers vowed to continue a nationwide strike after their latest round of pay negotiations with the government failed Thursday.

Government ministers and union leaders blamed each other for the lack of progress during more than two hours of talks. Teachers have been on strike since last week, closing most schools.

Prime Minister Mateusz Morawiecki appealed for teachers to end the strike, and invited teachers, parents and experts for negotiations April 26 on reforming the country's education system.

Striking teachers saw little chance for an agreement after the government insisted it doesn't have money to meet their demand for a 30% pay increase. The government is offering 15% raises starting in September and a smaller pay hike next year for an increase in the number of teaching hours.

"I don't believe that new proposals will be made on the government side," Magdalena Klein, a high school teacher from Chorzow, said on private TVN24.

The head of the prime minister's office, Michal Dworczyk, said it was crucial to have the strike suspended for matriculation exams starting May 6. The exams are the basis for university entry.

The strike has drawn support from many students, parents and artists. A rock concert was held Wednesday night in Warsaw in support of the strike.

Former president Lech Walesa has appealed to the teachers to end the strike, saying there was no sign that the right-wing government would make any concessions.

Many teachers in Poland earn less than supermarket cashiers. Their monthly earnings range from 1,800 zlotys to 3,000 zlotys ($470 to $780) a month, depending on experience.