Gabriel Resources said in a statement that if Parliament rejects the legislation, it would assess what recourse is open to it, including suing Romania for "multiple breaches of international investment treaties." The news sent the company's shares tumbling by 48 percent on the Toronto stock exchange.
The company also said it was urgently seeking confirmation of statements made in Bucharest and clarification of the impact on the project.
Anti-mine protesters have said the project would hand over Romania's assets to the Canadian company and the country would earn too little from the deal.
Ponta has acknowledged that his government could be sued by Gabriel Resources, but he said Monday that he and his Cabinet ministers don't want to be held responsible for "undermining the national economy."
President Traian Basescu and Ponta have accused each other of illicitly taking money to support the proposed mine. But Basescu, who once strongly supported the project, last week announced that he would take a neutral stance on the legislation.