Two unionized schools are among the 10 in the city set to begin a merit-pay plan next year, but the plan could face resistance from the union, the United Federation of Teachers.

A $10.5 million federal grant announced yesterday will pay for the program, which would reward teachers with up to $6,000 in bonuses if they raised student test scores or took on leadership positions.

All 10 schools set to participate are charter schools, but two — known as conversion schools — abide by UFT contracts. The group that will run the program, the Center for Educational Innovation, said the conversion schools’ involvement could lay the groundwork for expanding merit pay citywide. If union contracts are shown to permit the arrangement, and union members are shown to appreciate it, even traditional public schools could adopt it, the group’s project director, Frank San Felice, said.

But the union’s president, Randi Weingarten, yesterday suggested that might be impossible. She said unionized schools could not enact merit pay without renegotiating their contracts, a process the UFT could halt. “It has to be negotiated,” she said. “CEI or the school leadership is not going to unilaterally do this.”

Both the Center for Educational Innovation and a co-director of one of the schools disputed that yesterday. They said faculties at the two unionized schools, the Renaissance Charter School in Jackson Heights, Queens, and the John V. Lindsay Wildcat Academy Charter School in Manhattan, could amend their contracts to allow for merit-based pay without involving the union. Both faculties have already showed support for the program, in votes to join the grant application, they said.

“If our bargaining unit members decide that they want to participate in this, that’s their right,” Renaissance’s co-director of operations, Stacey Gauthier, said. She said she didn’t understand “why the union wouldn’t want to support their members getting extra income.”

Ms. Weingarten said she would support some types of performance-based bonuses, citing the union’s participation in an application to the same federal fund last year, which the city Department of Education also joined. The application called for a plan that would reward entire schools for meeting performance goals, but would not differentiate between teachers. It was not approved.

The new grant will distinguish between teachers; one of its bonuses would only go to a teacher who met his or her performance goals, representatives from the Center for Educational Innovation said.

Schools Chancellor Joel Klein, who supports bonuses for individual teachers, yesterday said he hopes the program can extend through the rest of city schools. “I hope Sy that your vision – that we’ll be able to extend it throughout the city,” he told the Center for Educational Innovation’s president, Seymour Fliegel.