* Says wins right to develop off-shore copper-gold project

* Says govt has option to joint venture on the project

TORONTO, Jan 17 (Reuters) - Nautilus Minerals said on Monday the government of Papua New Guinea has granted it a deep sea mining lease to develop its copper-gold project in the southwestern Pacific Ocean, sending its shares up more than 15 percent.

Toronto-based Nautilus, which is focused on exploring the sea floor for mineral deposits, said the 20-year lease covers an area of nearly 60 square kilometers around its Solwara 1 project.

The Papua New Guinea government has retained an option to take up to a 30 percent stake in the Solwara 1 project as a joint venture partner, the company said in a statement.

The option is exercisable within one month. If exercised the government will contribute funds to the project in proportion to its interest, including its share of the costs incurred to date, the company said.

Shares of Nautilus rose 35 Canadian cents to C$2.55 Monday morning on the Toronto Stock Exchange. (Reporting by Euan Rocha; Editing by Frank McGurty)