The Singapore Ministry of Foreign Affairs has reportedly served court papers relating to the dispute between PNG Sustainable Development Program Ltd and PNG's O'Neill Government on the State.
Under the rules of the Singapore Supreme Court, in which the case has been filed, the State has until February 17 to submit a response.
The SDP began the action in response to the government's move to take over the company's majority share, without compensation, in the lucrative Ok Tedi mine in Western Province, as well as its attempts to take control of SDP and the $US1.4 billion in the Long Term Fund.
The Singapore case is in addition to the company's decision to seek international arbitration for the return of the mine or compensation.
The request for arbitration has been formally accepted by the International Centre for Settlement of Investment Disputes in the US.