Aluminum Corporation of China, known as Chinalco, extended its bid for Mongolia-based coal producer South Gobi Resources Co amid uncertainty on local policies, Chinalco said in a statement on July 4.

Chinalco, the country's largest alumina producer, has placed a bid at C$8.48 ($8.35) per share, for 30 days, according to the statement.

Chinalco signed a lock-up agreement with Canadian international mining company Ivanhoe Mines, the largest shareholder of the Mongolian coal producer, which has an annual production capacity of 4.57 million metric tons of raw coal.

According to the agreement, Chinalco will buy the entire shareholding of Ivanhoe Mines for about $1 billion to acquire a majority stake in South Gobi Resources.

The Mongolian government is considering new foreign investment legislation in areas such as foreign ownership of Mongolian assets.

liuyiyu@chinadaily.com.cn