Although it enjoyed "de facto" independence, Dadra and Nagar Haveli were still recognised internationally (e.g. by the International Court of Justice) as Portuguese possessions. In 1961, amidst Indian preparation for the invasion of Goa, Daman, and Diu, K.G. Badlani, an officer of the Indian Administrative Service was, for one day, designated the Prime Minister of Dadra and Nagar Haveli, so that, as Head of State, he could sign an agreement with the Prime Minister of India, Jawaharlal Nehru, and formally merge Dadra and Nagar Haveli with the Republic of India. The Tenth Amendment of the Constitution of India was passed to incorporate Dadra and Nagar Haveli as a union territory, effective 11 August 1961. On 31 December 1974 a treaty was signed between India and Portugal on recognition of India's sovereignty over Goa, Daman, Diu, Dadra and Nagar Haveli. In December 2019, the Parliament of India passed legislation to merge Dadra and Nagar Haveli with the nearby union territory of Daman and Diu to create a single union territory to be known as Dadra and Nagar Haveli and Daman and Diu on 26 January 2020. Dadra and Nagar Haveli will be one of the three districts of the new union territory. The area of Dadra and Nagar Haveli is spread over . Its population density is . Though landlocked between Gujarat to the north and Maharashtra to the south, it is close to the western coast of India (between 20°0′ and 20°25′ N latitude and between 72°50′ and 73°15′ E longitude), and the Arabian Sea can be reached via Vapi in Gujarat. Dadra and Nagar Haveli comprises two separate geographical units. The larger part—Nagar Haveli—spans a roughly C-shaped area upriver from the city of Daman on the coast, at the centre of which, straddling the border with Gujarat, is the Madhuban reservoir. The smaller enclave of Dadra is a short distance to the northwest. Dadra and Nagar Haveli is in the middle of the undulating watershed of the Daman Ganga River, which flows through Nagar Haveli and later forms the short southern border of Dadra. The towns of Dadra and Silvassa lie on the north bank of the river. The Western Ghats range rises to the east, and the foothills of the range occupy the eastern portion of the district.