(Reuters) - Endeavour Mining <EDV.TO> will not share information vital to assessing its value until an extension to a deadline for making an offer for Centamin <CEY.L> is agreed, London-listed Centamin said on Wednesday.
Under English takeover law, Canada's Endeavour has until the end of December to make a firm offer for Centamin's assets.
Endeavour said on Monday the two firms had agreed to assess the feasibility of a merger, but analysts said then that it was clear the companies were not yet fully aligned.
Centamin, which called the Canadian miner's approach an "unsolicited offer", said both firms had agreed on "a reciprocal exchange of due diligence information" but Endeavour now said it would not provide information unless the deadline was extended.
The London-listed miner said in a statement on the merger plans that it was "disappointed that despite its efforts at constructive engagement, Endeavour has repeatedly refused to engage in a proper manner".
Centamin said its board believed Endeavour should enter into reciprocal due diligence without delay.
Endeavour did not immediately respond to Reuters' request for a comment.
"Without a tactical shift from one of the two sides, talks are going nowhere for now," Peel Hunt analysts wrote in a note.
Reflecting shareholder unease, Centamin shares dropped nearly 3% at the open but recouped some of those losses to trade down 1% by 0850 GMT. The stock surged 15% when Endeavour initially revealed the proposal.
Centamin said it would decide whether to seek a deadline extension after reviewing any information from Endeavour.
(Graphic - centamin, https://fingfx.thomsonreuters.com/gfx/buzzifr/15/3149/3149/Pasted%20Image.jpg)
(Reporting by Muvija M in Bengaluru and Barbara Lewis in London; Editing by Edmund Blair)