Pakistan has complained to UN chief Ban Ki-moon that the geographical coordinates notified by India of the Sir Creek estuary are "inconsistent" with international law and "impinge" upon Islamabad's territorial limits in the disputed area.
The complaint was made in a letter from Pakistan's mission to the UN which has been posted on the UN website.
It is in response to India's notifications specifying its geographical coordinates and boundary claims with regard to Sir Creek, which were placed on the website of the UN Division for Ocean Affairs and the Law of the Sea in May and November 2009.
The letter said India's "base points impinge upon Pakistan's territorial limits in the Sir Creek area and encroach upon its territorial waters, which are within its sovereign jurisdiction. This encroachment by India in Pakistan's limits is a grave violation of international principles."
It said Pakistan does "not recognise the baseline system promulgated" by India.
"While the Government of Pakistan reserves its right to seek suitable revision of this notification, any claim India makes on the basis of Indian notification to extend its sovereignty and jurisdiction on Pakistani waters or extend its internal waters, territorial sea, Exclusive Economic Zone and Continental Shelf is, therefore, not acceptable to Pakistan," the letter added.
The two countries had last year in May in Rawalpindi held their first round of talks in four years on the Sir Creek issue, focussing on the delimitation of the long disputed international maritime boundary.
Sir Creek is a 96-km estuary in the Rann of Kutch separating India's Gujarat state from Pakistan's Sindh province.