Rio Tinto chief executive Jakob Stausholm has refused to endorse a 2025 target for Africa’s Simandou province to start exporting iron ore, as softening prices for Australia’s most important commodity drove a 38 per cent slide in Rio’s full-year profit.

Confirmation that negotiations over the Simandou project were “taking a little bit longer” came as Rio posted $US13.27 billion of underlying earnings and joined rival iron ore miners BHP and Fortescue in making a discretionary cut to its dividend.