BHP (ASX: BHP) and unions representing workers at its Port Hedland iron ore operations in Australia have ended wage negotiations without reaching a new agreement, but further talks are scheduled for next week.

The miner has been negotiating with the Combined Ports Unions over a four-year enterprise agreement covering workers at Port Hedland, a key export hub in northwest Australia through which about $80 million of BHP’s iron ore shipments pass each day. Both sides said last week they had made progress in the negotiations.

A spokesperson for the Combined Ports Unions told Reuters that bargaining will resume next Tuesday. BHP did not reply to requests for comments. The Electrical Trades Union, one of three unions represented by the Combined Ports Unions, is also scheduled to meet separately with BHP negotiators on Thursday.

The negotiations are being closely watched because Port Hedland is one of the world’s largest iron ore export terminals and a critical link in BHP’s Pilbara operations. 

A prolonged labour dispute could disrupt exports from Australia’s biggest iron ore-producing region, although both sides continue to negotiate.