The move comes at a time when Indonesia has said it would stop nickel ore exports from Jan. 1, 2020, two years earlier than initially indicated, as it speeds up efforts to process more of its resources at home.

Nickel Mines, which currently owns 60% of HNI, said it would amend the agreement with partner Shanghai Decent Investment (Group) Co Ltd to limit its stake in the Rotary Kiln Electric Furnace (RKEF) plant to a maximum 80% from an earlier 100%.

RKEF is used for the smelting of ferronickel alloy.

Also, the period during which Nickel Mines can buy a further HNI stake has been extended by 10 months until Nov. 30, 2020.

Nickel Mines last month said it was increasing its stake in another Indonesian venture - Ranger Nickel Project - to 60% from 17% before Indonesia, the world's biggest nickel ore producer, expedited its exports ban earlier this month.

Shanghai Decent, which belongs to China's Tsingshan Group, the world's largest stainless steel producer, is a partner in both the Hengjaya and Ranger projects.

(Reporting by Aby Jose Koilparambil in Bengaluru; editing by Richard Pullin)