Anglo-Australian miner Rio Tinto (ASX: RIO) falls short of 50 percent votes it needs later today in order to acquire Riversdale Mining, a coal producer focus on South Africa. This comes after the company continues to attract approvals for its $4 billion bid to obtain authority over the mining corporation.

Rio Tinto accounted today a 1.28 percent increase in interest and approval on its intended takeover of the Riversdale Mining. Its acceptance rate has increased from 38.38 percent last week to this day’s 39.66 percent.

After increasing its offer to $16.50 dollars per share earlier this month, the mining magnate has extended its deadline four times since they initiated the bid on December 2010. Rio declared an offer slip back to $16 per share if it does not get the needed 50 percentage approval late this day and keep the proposal open until April 6, except an extension is called for.

The Riversdale branch based in Sydney is largely controlled by two steel companies: the Cia Siderurgica Nacional of Brazil with 19.9 percent of its shares and India’s Tata Steel with 27.1 percent. Combined they hold a total of 47 percentage potion of Riversdale which is now runs a coal mine in South Africa and building on two coal mining ventures in the nearby region of Mozambique.