A week-long strike by more than 30,000 Los Angeles teachers that has disrupted classes for nearly half a million students neared an end on Tuesday as the teachers' union and the second-largest US school district reached a tentative contract deal.

A union leader said the negotiations, including an all-night session that ended around dawn on Tuesday, addressed many of the teachers' demands including a pay rise and provisions to hire additional support staff including librarians, nurses and counsellors.

"I'm proud to announce, pending approval, that we have an agreement that will allow teachers to go back to work on their campuses tomorrow," Mayor Eric Garcetti, who has mediated the talks, said at a news conference.

He was joined by Alex Caputo-Pearl, the president of the United Teachers Los Angeles union, and Austin Beutner, the superintendent of the Los Angeles Unified School District.

Precise terms of the deal will be disclosed later once they have been presented to union members ahead of a ratification vote, which union leaders said could be completed within hours.

Officials said the negotiations resulted in two back-to-back contracts. The first, which expires in June, will include the salary raise. Other provisions will be contained in a second, three-year contract, to follow.

Teachers walked off the job on January 14 in their first strike in three decades against the school district, demanding higher pay, smaller class sizes and the hiring of more support staff in the district's roughly 1,200 schools.

Caputo-Pearl, the union president, said more details would be released later. Union members will vote on whether to approve the deal on Tuesday; if they ratify it they will return to work on Wednesday.

"So many schools have gone without for so long, and now they'll have these crucial services," Caputo-Pearl said at the news conference.

Reawaken the public

The union also sought restrictions on the steady expansion of independently managed charter schools, arguing they divert resources from traditional classroom instruction for the bulk of the district's students.

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The leadership of the school district - an independent body that does not answer to the Los Angeles mayor - had said throughout the talks that they largely supported the union's goals but that they did not have enough of a budget to cover the demands.

Union supporters, and even school district officials have credited the striking teachers with helping reawaken the public, the media and politicians around the country to widespread difficulties facing schools in California and elsewhere.

Teachers staged walkouts over salaries and school funding in several US states last year, including West Virginia, Oklahoma and Arizona.

The Los Angeles stoppage differs in that educators face a predominantly Democratic political establishment more sympathetic to their cause.

Labour tensions are still simmering in other big-city school districts. The teachers' union in Denver held a strike authorisation vote on Saturday after rejecting a contract offer. Results will be announced on Tuesday.