(Sharecast News) - Plastic packaging specialist RPC Group has again pushed back the deadline for private equity firm Apollo Global Management to make a takeover offer.Apollo had been due to announce a firm intention to make an offer for the company on Friday, but RPC said that the Panel on Takeovers and Mergers had extended the 'put up or shut up' deadline to 1700 GMT on 18 January in order for discussions to continue.Noting that Apollo has had access to its books since the talks about a potential offer began, RPC said: "Discussions are well advanced and Apollo has confirmed to RPC that its diligence is now substantially complete."Talks have been going on for well over three months now, with RPC confirming in early September that it was speaking to Apollo and another private equity group, Bain Capital.The deadline for firm offer to be made was extended into October and then again into November, before Bain dropped out of the race at the start of December.RPC has come under pressure from investors over its growth plans and appropriate level of debt. Chairman Jamie Pike said in the summer that "differing investor views on the appropriate level of leverage is constraining the group's ability to pursue some attractive opportunities for growth".Earlier this month, the FTSE 250 group said it had completed the sale of two out of the three non-core disposals it was planning.RPC shares were up 1% to 676.8p in early trading on Friday. "It may be hope over expectation that the tone of the statement appears more positive and pointing towards a deal," said broker Peel Hunt."Apollo has had access to due diligence materials, which means that it does not have issues with the numbers at this point even if it ultimately walks away. The discussions are described as well advanced and that Apollo has confirmed to RPC that its diligence is now substantially complete.""The key factor is price and that we can only guess at (900p?) but the fact the two sides are still talking is a positive. There is also the Bain factor - if Apollo makes an offer, it can come back into the process. Another month to wait but 18 January now appears to be the final deadline."