The territorial disputes of India and Nepal include Kalapani 400 km2 at India-Nepal-China tri-junction in Western Nepal and Susta 140 km2 in Southern Nepal. Nepal claims that the river to the west of Kalapani is the main Kali river; hence the area should belong to Nepal. But India claims that the river to the west of Kalapani is not the main Kali river, and, therefore the border there should be based on the ridge lines of the mountains Om Parvat to the east of the river. The river borders the Nepalese province of Sudurpashchim and the Indian state of Uttarakhand. The Sugauli Treaty signed by Nepal and British India on 4 March 1816 locates the Kali River as Nepal's western boundary with India. Subsequent maps drawn by British surveyors show the source of the boundary river at different places. This discrepancy in locating the source of the river led to boundary disputes between India and Nepal, with each country producing maps supporting their own claims. Indian government, however, from 1962 onward, forwarded the argument that border should be based on the ridge lines of the mountain Om Parvat. The Kali River runs through an area that includes a disputed area of about 400 km2 around the source of the river although the exact size of the disputed area varies from source to source. The dispute intensified in 1997 as the Nepali parliament considered a treaty on hydro-electric development of the river. India and Nepal differ as to which stream constitutes the source of the river. Nepal has reportedly tabled an 1856 map from the British India Office to support its position. Kalapani has been controlled by India's Indo-Tibetan border security forces since the Sino-Indian War with China in 1962. In 2015, the Nepalese parliament objected an agreement between India and China to trade through Lipulekh Pass, a mountainous pass in the disputed Kalapani area, stating that the agreement between India and China to trade through Kalapani violates Nepal's sovereign rights over the territory. Nepal has called for the withdrawal of the Indian border forces from Kalapani area.