Relations between miners Centamin and Endeavour Mining appear to remain strained, as the companies try to make headway with negotiations about a potential merger, which would create a mining company producing more than one-million ounces a year.

Initial exchanges between the companies do not appear to have started on good terms, with LSE- and TSX-listed Centamin complaining that its potential suitor is refusing to engage in a proper manner, while TSX-listed Endeavour says Centamin is not prepared to enter into constructive engagement.

Endeavour went public with its C$2.5-billion all-share proposal in early December, and now only has until the end of this month to make an announcement about an intention of a firm offer under the UK’s takeover rules.

Claiming that Centamin is not engaging meaningfully, Endeavour said on Thursday that there was not sufficient time left before the “put up or shut up” (PUSU) deadline to complete a reciprocal due diligence – an exercise both companies agreed on at a meeting last week.

The company wants the deadline extended by one month to January 31.

“Endeavour will only proceed if it can complete a proper and comprehensive due diligence exercise, including technical analysis and site visits,” Endeavour said in a statement, which it issued in response to Centamin’s press release of Wednesday that urged its potential suitor to enter into substantive reciprocal due diligence, without further delay.

Centamin claimed that Endeavour would not provide it with required information, such as its financial model, without it agreeing to an extension of the PUSU, while it argued that it would only decide on an extension, once it could review forthcoming information from Endeavour.

Endeavour said on Thursday that it had made a number of concessions, including signing a non-disclosure agreement and standstill in good faith to make progress with merger negotiations.

“Endeavour continues to believe in the strategic merits of the combination for both sets of shareholders, and therefore urges Centamin to request that the Takeover Panel consents to an extension of the current PUSU period to January 31, 2020, to enable completion of the necessary reciprocal due diligence exercise, which cannot realistically be completed in seven working days.”