Calvary will take legal action against the ACT government over the forcible acquisition of its Bruce public hospital.
The territory's parliament is expected to pass legislation on Wednesday to allow the government to compulsorily acquire the hospital from July 3.
Calvary had sought to renew negotiations with the government over the future of the Bruce site but the organisation said no meaningful options had been considered.
The government's legislation said Calvary would be paid compensation based on "just terms" but Calvary national chief executive Martin Bowles said he did not believe this was available under the proposed legislation.
"Our review of the proposed legislation and associated regulation indicates that just terms are simply not available and outside of this there is no indication that commercial terms are available to resolve this matter," he said.
"All we have is an announcement and an imposed unrealistic timeline that has distressed our people and could ultimately put clinical safety at risk."
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The forced acquisition is the biggest in the history of ACT's self-government and came after negotiations between the government and Little Company of Mary, the organisations that runs Calvary, broke down.
The negotiations were centred around a proposed new hospital for Canberra's north. The government wanted the hospital to be built on the Calvary site.
The government and Calvary could not agree on the time frame of a new agreement. The government wanted a new 25-year agreement with the organisation but Calvary wanted to retain its current contract, which has 76 years remaining.
Calvary will not provide details of the court action it intends to take, however, an injunction is the most likely option.
The organisation is not able to pursue this until the bill has passed the Assembly.
Health Minister Rachel Stephen-Smith said, earlier on Tuesday, she was confident the government's legislation would be able to stand up to any legal challenge.
"We absolutely understand that it is possible that Calvary will seek to escalate this to some kind of legal action and we're fully prepared to respond if that is the case," she said.
But Ms Stephen-Smith said she encouraged Calvary to think of the staff at the hospital and to work with the government on the acquisition.
"My message to Little Company of Mary would be to think about the staff and the consumers in the ACT and the need to provide certainty and a smooth transition. We are very confident that our legislation will stand up to any challenge," she said.