(Adds Mitsui statement, background)
Jan 29 (Reuters) - Japan's Mitsui & Co 8031.T has made a $481 million offer to buy Australia's AWE Ltd AWE.AX , trumping bids from two other companies that are all vying for a stake in the promising onshore Waitsia gas field.
The Mitsui offer of A$0.95 per share in cash, or about A$594 million, is at an 11.8 percent premium to the closing level of AWE stocks on Thursday.
It is also significantly higher than a sweetened $403 million takeover offer from Mineral Resources Ltd MIN.AX , which AWE accepted in December, and another bid from a Chinese state-owned firm. said the Mitsui proposal was subject to, besides other conditions, the company terminating its scheme implementation agreement with Mineral Resources by the end of Feb. 2.
The Mitsui offer, however, is not contingent to a demand to inspect AWE's books, or regulatory and internal approvals, AWE said in the statement on Monday.
Mitsui in a separate statement said it had received approval from Australia's foreign investment regulator for the proposal.
"AWE's interest in the Waitsia Gas Project has the potential to be an attractive source of future gas supply to a wide range of Western Australian gas customers," Mitsui said. ($1 = 1.2340 Australian dollars)