(Adds background, details on previous bids and share movement)
Jan 31 (Reuters) - AWE Ltd AWE.AX said on Wednesday it has given suitor Mineral Resources MIN.AX three days to match a A$594 million ($480 million) takeover offer from Mitsui & Co 8031.T , or it will nominate the Japanese bid as a superior offer.
The Australian gas producer said in a statement it notified Mineral Resources late Tuesday, giving it a deadline of Friday, Feb. 2 to match the Mitsui proposal, which was 14.5 percent above the Mineral Resources offer.
AWE said it would enter into a bid implementation deed with Mitsui and recommend its bid to shareholders if Mineral Resources did not match the A$0.95 a share offer.
Investors, however, are eyeing a higher offer emerging, with AWE's shares currently trading at A$0.9725 a share. Resources was not immediately available for comment on Wednesday, but a spokesman said in an emailed statement on Monday that the company was looking at Mitsui's proposal and considering its position.
Mitsui's offer on Monday marks the first full takeover bid by the Japanese trading giant for an Australian company.
State-owned China Energy Reserve and Chemicals Group (CERCG) had also bid for AWE last November, although its offer was later topped by Mineral Resources.
AWE owns a 50 percent stake in the prized Waitsia gas prospect in Western Australia.
($1 = 1.2370 Australian dollars)