LOS ANGELES (Reuters) - A union representing more than 30,000 Los Angeles teachers on Wednesday postponed until next week a threatened strike over lingering contract negotiations with the country’s largest school district, citing a last-minute legal snag.

United Teachers Los Angeles had called a strike for its members in the city’s 900 public schools for Thursday if an agreement was not reached before then over such issues as pay, staffing, and class sizes.

But the teachers union delayed the walk-out after officials with the Los Angeles Unified School District said they had not been given a legally required 10-day notice of the labor action. A judge refused to rule on that issue on Wednesday, saying that the UTLA’s court papers had been incorrectly filed.

“While we believe we would eventually win in court against all of (schools superintendent) Austin Beutner’s anti-union, high-priced attempts to stop our legal right to strike, in order for clarity and to allow members, parents, and our communities to plan, UTLA is moving the strike date to Monday, January 14,” union president Alex Caputo-Pearl said in a written statement.

Beutner, who was in the state capitol, Sacramento, on Wednesday, said in a written statement that district officials were doing their best to avert a strike.

“We are building support at the state level to find more resources to help our students and better support all who work in our schools,” Beutner, a former publisher of the Los Angeles Times, said in the statement.

A second court hearing has been scheduled for Thursday over the 10-day notice as negotiators for the two sides met separately at the bargaining table to make another attempt at hammering out a new contract. Negotiations have dragged on since April.

The union is calling for a 6.5 percent pay raise, more librarians, counselors and nurses on campus, smaller class sizes and less testing, as well as a moratorium on new charter schools.

Negotiators for the Los Angeles County School District, which educates some 600,000 students, have countered with a proposed 6 percent salary hike with back pay and $100 million investment to hire more staff and decrease class size.The district has urged teachers not to strike, saying that it would hurt students who returned from winter break only on Monday.

In the event of a walkout, district officials have said they would be able to fully staff classes with administrators and substitute teachers.