(Sharecast News) - Ophir Energy has extended the deadline for Indonesian oil and gas producer Medco Energi Internasional to make a firm takeover offer or walk away from a deal, the company reported on Monday.Medco now has until 1700 GMT on Thursday 31 January to make its decision, as discussions between the two companies over a possible acquisition offer for Ophir at 55 pence per share continue.The London-listed company rebuffed a proposal at 48.5p per share, which valued Ophir at around £343m, earlier in January, arguing that it undervalued the company and that Medco had initially proposed to move for 58 pence per share.Ophir's move towards a sale follows warnings of a $300m write-down for the full-year as its shares lost almost half their value following the company's unsuccessful financing of a liquefied natural gas project in Equatorial Guinea, leading to the subsequent loss of its licence for the project.Research firm WoodMac said that the acquisition of Ophir's current output of 25,000 barrels per day of oil equivalent would make the ambitious Medco the seventh largest non-national oil company upstream producer in Southeast Asia.Ophir Energy's shares were up 6.65% at 50.50p at 1642 GMT.