Melbourne, Australia — MININGREVIEW.COM — 11 March 2011 – Global mining giant Rio Tinto raised its offer for Mozambique-focused coal miner Riversdale Mining to US$3.9 billion in a final bid to woo key shareholders who have held up the deal, and to gain control of coveted coal assets.

Reuters reported from here that investors doubted the move would be enough to secure the 50.1% acceptances Rio wanted, and sent Riversdale’s shares down as much as 2.4%.

“The market’s clearly a bit skeptical that it will get across the line,” said Peter Chilton, an analyst at Constellation Capital Management, which owns shares in Rio Tinto.

Rio Tinto raised its offer price by 3% to A$16.50 per share yesterday and extended the offer period for the third time, to 1 April, but said the new offer was its final one if there were no competing offers.

Standing in Rio’s way are India’s Tata Steel , the world’s No. 7 steelmaker, and top Brazilian steel producer CSN , who have increased their stakes in Riversdale since the bid and now hold a combined 47%. So it would need nearly 100% acceptances from the rest of Riversdale’s shareholders to gain majority control. “It’s going to be quite hard,” Chilton said.