Nigeria’s state oil company said on Tuesday it will increase its stake in a Chevron-operated gas-to-liquid refinery to 60% as part of a cost dispute resolution with the U.S. oil major.

The Nigerian National Petroleum Corporation (NNPC) has a 20%stake in the plant some 60 miles (100 km) southeast of Lagos.

California-based Chevron, which is trying to sell some Nigerian assets in an effort to focus on its fast-growing U.S. production, did not immediately comment.

The 33,000 barrel-per-day (bpd) plant, which produces synthetic diesel, liquefied petroleum gas and naphtha from natural gas using technology from South Africa’s Sasol, cost around $10 billion to build, four times the original estimate, and its start-up in mid-2014 was years late.