State refiner Kuwait National Petroleum Company (KNPC) plans to upgrade its Mina Abdullah and Mina Al Ahmadi refineries with up to KD5 billion ($19 billion), state news agency Kuna said.

The tender would be launched in August after winning approval from Kuwaiti authorities, KNPC's deputy chairman Asaad Al-Saad told Kuna late on Monday.

Saad said KNPC wanted to upgrade the capacity of its Mina Abdullah and Al Ahmadi refineries to 800,000 barrels per day from 600,000 bpd by adding new units or improving existing ones.

The project's cost would range between KD4 billion and KD5 billion, up from an initial estimate of KD1 billion in 2003, he said.

The refinery upgrade, which is due to take effect after closure of the ageing Shuaiba refinery in 2011, is part of plans by the major Opec producer to raise refinery capacity to 1.415 million bpd from 930,000 bpd.

KNPC is also due to announce the winners for a tender to build a 615,000 barrel per day (bpd) refinery, the world's biggest refinery project.

Kuwait, the world's seventh-largest oil exporter, has said that more than 10 firms presented bids for the refinery's five packages, among them Italian, French and U.S. companies.

KNPC has delayed the tender several times and more than doubled the budget to $14 billion amid spiralling costs in the oil industry.-Reuters