OSLO (Reuters) - Norway's top political parties are open to a merger between fertiliser firms Yara (>> Yara International ASA) and CF Industries (>> CF Industries Holdings, Inc.) but the Norwegian state must own at least 34 percent of the merged firm, party officials told Reuters on Tuesday.

The merged entity must also keep its headquarters in Norway, top officials from the Conservatives, Labour, Progress and Centre parties said separately. Together these parties have a large majority in parliament.

Yara and CF announced on Tuesday that they were in preliminary talks about a merger of equals.

The government now owns 36.2 percent of Yara and a government white paper published in June stipulates that the state should hold no less than 34 percent in the firm.

(Reporting by Gwladys Fouche, Ole Petter Skonnord and Joachim Dagenborg; Editing by Balazs Koranyi)

Stocks treated in this article : CF Industries Holdings, Inc., Yara International ASA