Petaquilla formally rejected the "hostile" bid as inadequate on Monday, but Inmet said in a statement that the rejection contained no information that would cause it to change the offer made in early September.
"It is important to note that over five weeks have passed since Inmet publicly announced its intention to make an offer for Petaquilla, and Petaquilla's management has provided no viable alternative," said president and CEO Jochen Tilk.
"During the limited interaction between Petaquilla and Inmet, Petaquilla management showed no interest in pursuing Inmet's offer on a friendly basis. Given the status of these interactions and the absence of a viable alternative, shareholders should consider the impact on the Petaquilla share price in the event the Inmet offer does not proceed."
Petaquilla's stock shot up some 60 per cent after the Inmet offer of 48 cents per share in cash — or 0.0109 of an Inmet share for each Petaquilla share — in a bid to consolidate the area around its Cobre Panama project.
The issue closed at down a penny at 62 cents Monday on the Toronto Stock Exchange.
Petaquilla said in its statement that the Inmet offer failed to provide adequate value to shareholders and had been unanimously rejected by company's board.
"In particular, the Inmet offer does not adequately reflect Petaquilla's current value or the value of Petaquilla's substantial growth prospects, nor does it take into account the true value of Petaquilla to Inmet and its shareholders," executive chairman Richard Fifer said.
Petaquilla's Molejon project neighbours Inmet's US$6.2-billion Cobre Panama copper-gold porphyry project, Panama's largest-ever mine development.
Inmet said Tuesday that Petaquilla continues to "incorrectly suggest that Inmet requires Petaquilla's agreement to develop Cobre Panama."
"Contrary to this assertion, Inmet's subsidiary Minera Panama S.A. requires no agreement from Petaquilla, has received all required permits to commence construction, and has been under full construction since May this year."
Tilk added that the Inmet bid — a 37 per cent premium to Petaquilla's share prior to the offer — is the most attractive alternative for Petaquilla's shareholders.
"However, the outcome of this offer is not material to the development of Cobre Panama and Inmet is therefore prepared to let the offer expire."
In addition to Cobre Panama, Inmet produces copper and zinc at its operations in Turkey, Spain and Finland.