The company was also pursuing other strategic alternatives and possible business combinations, which it hoped might present better value for shareholders than Inmet's C$2,00 a share offer, which closes on September 3, PTC said.
Inmet expects that a successful bid for PTC would enable it to speed up the development of the company' large Petaquilla copper project in Panama.
Inmet, which owns 48% of the project, said in April that the project would likely face delays, after PTC filed a request for arbitration with base-metals miner Teck Cominco, claiming that the larger firm had failed to meet certain conditions to take a stake in the project and that Teck's interest in the project had expired, leaving Inmet and PTC as the only two stakeholders.
Inmet has indicated that it would back Teck Cominco in the dispute, and Teck has also expressed its support for Inmet's plans to buy PTC.
However, PTC said on Tuesday that Inmet's offer valued the company based on its 26% holding in the Petaquilla project, and did not take into the account that it could win in arbitration, and would therefore own 52% of the project.
The offer was also based on “outdated and incomplete data”, PTC said.