(Changes company ownership in second paragraph to South32 from BHP Billiton)
BOGOTA, May 31 (Reuters) - Union workers at Colombia's Cerro Matoso mine, one of the world's largest producers of ferronickel, will begin an indefinite strike on June 14 in protest over work and pay conditions, the union president said.
A strike at Cerro Matoso, owned by Australia's South32 Ltd, could impact global nickel prices as production stalls. Miners last year went on strike at the mine for two weeks before reaching agreement on a dispute that had forced previous owner BHP Billiton to declare force majeure.
"The union has voted to strike on June 14 because of the negative attitude of the company to resolve workers' demands," Domingo Hernandez, president of the Sintracerromatoso union, told Reuters.
"Despite the decision to strike, we maintain an open door to dialog. A solution to avoid the strike lies with the company."
Company representatives were not immediately available for comment.
Workers have demanded a pay increase of 9.77 percent, Hernandez said.
The mine, located in the northern province of Cordoba, produced 36,670 tonnes of ferronickel last year, down 11 percent from 2014.
Cerro Matoso has more than 1,200 employees, 520 of whom belong to the union. (Reporting by Luis Jaime Acosta; Writing by Helen Murphy; Editing by Alan Crosby)