Global mining giant Rio Tinto seems to be inching closer to an acquisition of Australian firm Riversdale, with the company on Wednesday announcing it has increased its stake in the target company by 0.95 per cent to 35.89 per cent in the last two days.

“The number of Riversdale shares in which Rio Tinto Jersey Holdings and its associates have a relevant interest has changed from 34.94 per cent to 35.89 per cent,” the company said in a filing to the Australian Stock Exchange.

In December, Rio had put in a takeover bid of AU$ 16 per share for Riversdale, valuing the company at AU$ 3.9 billion. The offer was also recommended by the Australian firm’s board in January.

Early this month, the offer was increased to AU$ 16.50 per share if Rio gets an over 50 per cent stake in Riversdale by today (March 23). Subsequently, the company extended this deadline further to March 28 on Monday.

The company also extended its offer period for the fourth time to April 6 at AU$ 16 per share.

“The additional time would allow some investors to finalise the unwinding of equity swaps, or settle trades that have occurred on the Australian Securities Exchange before they can accept the offer,” the company had said.

However, the two largest shareholders of Riversdale — Tata Steel and Brazilian steel-maker Companhia Siderurgica Nacional (CSN) — have not yet responded to Rio’s offer positively.

Both the companies have maintained that they are more interested in getting coal rather than making a quick gain and would stay invested in Riversdale, which has about 13 billion tonnes of rich coking and thermal coal reserves in Mozambique.

The two firms together hold an over 47 per cent stake in the Australian mining firm, which has about 13 billion tonnes of rich coking and thermal coal reserves in Mozambique.