For decades, India has refused to recognize the Pakistan-China border in a disputed part of the Himalayas.
But last week, Pakistan and China formalized a border crossing in a remote part of the mountainous region.
A sharp reaction was given to this from India.
Both countries have signed the Pakistan-China Border Joint Commission. Pakistan has described it as an "important milestone" that will deepen cooperation on border management, trade and connectivity between India's regional rivals.
India rejected this move as legally baseless. India has said that it does not recognize any Pakistan-China border located in that area.
This announcement has come at a very sensitive time.
India and China are trying to stabilize their relations after years of military tension on the Line of Actual Control (LAC).
LAC is the disputed line separating the armies of the two countries on most of the Himalayan border.
On the other hand, China and Pakistan are also increasing cooperation on the neighboring part of the border on which India claims.
Indian Foreign Ministry spokesperson Randhir Jaiswal said, "There is no border between Pakistan and China. We reject the so-called Joint Commission, which has no legal basis."
This commission is related to the Pakistan-China border, which also includes the Shaksgam Valley. This is an area of about 5,180 square kilometers. Pakistan handed over this area to China in 1963. However, India considers it part of its territory in Ladakh.
India says that this area was part of the former princely state of Jammu and Kashmir and was illegally occupied by Pakistan before being handed over to China. The Government of India has never recognized this agreement and considers it illegal and invalid.
This history shows the special sensitivity associated with Wednesday's announcement.
The Indian Ministry of External Affairs said, "Pakistan has no right to make any arrangement with respect to the territory of India which it has illegally and forcibly occupied."
Pakistan says that Jammu and Kashmir is still a disputed territory and hence India has no right to challenge Pakistan's 1963 border agreement with China. Pakistan considers this agreement as valid.
Jabin T. Jacob, professor in the Department of International Relations and Governance Studies, Shiv Nadar University, Delhi, said that this new development is a sign of reactivation of an old system rather than a completely new system.
He told the BBC, "There is a provision for a Joint Border Commission in the China-Pakistan Agreement of 1963. The only issue at this time is to bring it into operation."
He said that there could be many reasons behind its timing.
He said these could include China's broader efforts to demarcate its borders and its desire to institutionalize cross-border contact and movement, at a time when conflict and instability continues on Pakistan's other borders.
Jacob said India should be "concerned" about this development. He said that more importantly, this step seems to ignore a provision of the 1963 treaty itself.
According to Jacob, Article 6 of the agreement provided that after the Kashmir dispute was resolved, the agreement would be renegotiated with the country that would ultimately control the region.
Jacob said that the problem for India increases due to the international information environment.
He said, "China has a relatively strong position in the field of international media and information. India's position is limited in comparison to its presence on CGTN, CRI and social media. This allows China to present its position and map to the world, while India's reaction is limited to just expressing anger, which the rest of the world will probably ignore."
This concern is separate from the practical management of the border. Pakistan and China already have extensive infrastructure and connectivity in this region.
This includes the China-Pakistan Economic Corridor (CPEC) and the Karakoram Highway.
Hussain Haqqani is the former ambassador of Pakistan to America. Haqqani is now a senior fellow at the Anwar Gargash Diplomatic Academy and the Hudson Institute.
He says that the new commission is both practical and political.
"It is a mechanism to enhance border and border cooperation, prevent illegal infiltration and protect strategic infrastructure related to CPEC," Haqqani told the BBC.
He said that this also gave an indication to India that Beijing sees Kashmir from the Pakistani perspective only.
Haqqani says, "China has never accepted India's stand on Kashmir and China looks at Gilgit-Baltistan from the Pakistani perspective, not from the Indian perspective."
Haqqani said that Islamabad's stance has changed in response to the developments in Indian-administered Kashmir.
He said, "Pakistan still maintains that the final status of Jammu and Kashmir has not been decided yet. But India has made internal changes in its part of Kashmir. For example, Article 370 has been abrogated. Therefore, Pakistan does not see any problem in institutionalizing the actual situation that has been with China since 1963."
For China, this arrangement also fits into a broader pattern of using its relations with neighboring countries to manage and signal its position towards India.
Haqqani said that giving assurance to Pakistan on Kashmir issue is strategically and geopolitically important for China.
Haqqani says, "On the strategic front, it deepens relations with Pakistan and on the geo-strategic front, it strengthens India's fear of a double front threat from China and Pakistan. It pleases Pakistan and benefits China."
Experts say that the timing of this statement is also important.
Haqqani says, "China always plans its decisions months, if not years, in advance, so the decision to operationalize the Joint Border Commission must have been taken some time ago."
"This information was released after President Xi Jinping's recent BRICS summit visit to send a message of assurance to Pakistan in the strategic partnership and to remind India that nothing changes China's approach towards South Asia."
But Jacob warned that every aspect of the incident should not be seen as direct military action against India.
He said, "At present there is no immediate or obvious impact on the LAC."
This suggests that the significance of last week's announcement may lie more in the institutionalization of arrangements that India has consistently rejected than in immediate changes to the disputed Himalayan border.
Randhir Jaiswal said India's position remains "clear and consistent", adding, "Any attempt by Delhi to legitimize Pakistan's illegal occupation of Indian territory is unacceptable and has no impact on India's sovereignty."
