Pakistan's Baluchistan province has objected to a mining lease being sought by a joint venture between Antofagasta and Barrick Gold, further delaying a major planned copper and gold project in the country's southwest.

London-listed Antofagasta and Canadian group Barrick Gold are partners in the Tethyan Cooper Co (TCC) joint venture which has a 75 percent interest in the Reko Diq project and submitted an application for a licence in February.

Samia Ali Shah, a spokeswoman for TCC which has been meeting Pakistani officials in recent months in the hope a decision would be reached in September, said Baluchistan had raised objections to its application for a mining licence.

We have been asked to reply to the observations raised by government of Baluchistan within 30 days, she said.

Baluchistan officials were not available to comment.

Antofagasta and Barrick spent $200 million in 2006 buying the exploration licence from rival BHP.

Reko Diq -- which will be only the second significant project in the mineral-rich region, along with smaller, Chinese-operated Saindak -- holds an estimated 5.9 billion tonnes of mineral resources, with an average copper grade of 0.41 percent and an average gold grade of 0.22 grams per tonne.

The $3.3 billion project has faced difficulties since last year when Baluchistan said it would cancel the project amid growing anger over outsiders exploiting natural resources in Pakistan's biggest and poorest province.

Baluchistan was initially barred by Pakistan's supreme court from giving approval until a separate investigation over the awarding of the concession to TCC was over. In May, the court said the provincial government could decide on the lease.

If approved, the Reko Diq will mark the largest foreign direct investment into Pakistan mining and a major investment in Baluchistan, which TCC said could transform the region. At its peak, it is likely to employ 11,000 people.

Separatist guerrillas in Baluchistan, on the border with Afghanistan and Iran, have for decades been fighting a low-level insurgency for control of provincial gas and mineral resources, which they say are unfairly exploited by the country's richer and more powerful provinces.

The project, which will produce 200,000 tonnes of copper and 250,000 ounces of gold per year, will no longer begin production in 2015, as envisaged earlier. The date has been pushed back a year or two due to delays over the mining licence.