Striking S.Africa building workers say near deal

* Unions willing to agree under conditions

* To meet with employers at 0800 GMT

JOHANNESBURG, July 14 (Reuters) - South African construction workers are near a deal with employers to end a strike that is holding up work on stadiums for the 2010 World Cup, the main union involved in the dispute said on Tuesday.

National Union of Mineworkers spokesman Lesiba Seshoka said it would only agree to the latest pay offer of an 11.5 percent increase under certain conditions, but declined to say what those were.

"Our members are willing to accept the offer on certain conditions, which the employers have to meet," he said.

The union is due to meet employers at 0800 GMT.

The pay strike, which started last week Wednesday, has stopped work at stadiums for the World Cup and on the mass transit Gautrain high-speed rail project, serving the area around Johannesburg.

The industrial action also poses a challenge for President Jacob Zuma, who has little room to meet the demands of union allies flexing their muscles since he took office in May.

The National Union of Mineworkers, which has been demanding a 13 percent wage rise, has said 70,000 workers are affected by its strike. It only affects building workers represented by the union and not miners.

A spokesman for the smaller Building Construction and Allied Workers' Union, Narius Moloto, said he also believed a resolution to the dispute was close.

"We think we are very close to a deal... it will be up to the employers to make a deal this morning," he said.

Major construction firms include Murray & Roberts Holdings Ltd (MURJ.J), WBHO (WBOJ.J) and Group Five (GRFJ.J). (Reporting by Alison Raymond; writing by Agnieszka Flak; editing by Matthew Tostevin)