The standoff between India and China escalated after Beijing said Monday that the Indian Army objecting to its constructing a road in an area near Sikkim was a "betrayal" of the stance taken by successive Indian governments and said India must withdraw from the region.
China and India have been engaged in a standoff in the Doka La area near the Bhutan tri-junction for almost a month.
Doka La is the Indian name for the region which Bhutan recognises as Dokalam. China claims Doka La is a part of its Donglang region.
Chinese foreign ministry spokesman Geng Shuang accused India of violating the existing convention between the two countries on demarcation of boundaries.
"By entering into the Chinese territory and obstructing Chinese troops' normal activities, India violated the existing convention on the boundary and basic principle of the international law and obstructed peace and stability of the boundary area," Geng told the press. "We require the Indian side to withdraw their troops to the Indian
side of the boundary and create conditions for the restoration of peace and stability in the relevant areas."
"The India-China boundary in the Sikkim section is well demarcated. The action taken by India is a betrayal of the position taken by (successive) Indian governments," he said.
"What has happened is very clear, the Sikkim section of the boundary has already been defined by the 1890 convention between Great Britain and China. Doklam belongs to China."
"Former Indian Prime Minister Jawaharlal Nehru endorsed the 1890 Sino-British Treaty on Sikkim in a letter to then Chinese counterpart Zhou Enlai in 1959. Successive Indian governments have also endorsed this," he said.
The Chinese foreign ministry also dismissed Defence Minister Arun Jaitley's remarks that India of 2017 was different from what it was during the Indo-China war in 1962, stating that Beijing will take "all necessary measures" to safeguard its territorial sovereignty.
Since the standoff on June 6, when PLA bulldozers destroyed bunkers of the India Army claiming the area belonged to China, Chinese media have carried several pieces warning India for escalating border tension and "reminding" the Indian Army about the 1962 war.
Responding to China's oblique reference to the war fought 55 years ago, asking India to learn from "historic lessons", Arun Jaitley had said, "If they are trying to remind us, the situation in 1962 was different and India of 2017 is different."
He had also said the current standoff between Indian and Chinese troops in the Sikkim sector was triggered by Beijing.
Responding to Arun Jaitley's remarks, Chinese foreign ministry spokesman Geng Shuang said, "He is right in saying that India in 2017 is different from 1962, just like China is also different."
Sikkim, which became a part of India in May 1976, is the only state with a demarcated border with China. The lines are based on an 1898 treaty signed with China.
Asked if there was a possibility of a meeting between Prime Minister Modi and Chinese President Xi Jinping during the G20 Summit in Hamburg in Germany this
week, Geng said he has "no information at the moment" about the arrangements for bilateral meetings between Xi and leaders of other countries.
He, however, said the line for diplomatic communication between India and China is "open and smooth".
India's National Security Adviser Ajit Doval, who is the Special Representative for the India-China border talks, is to visit Beijing on July 26 to attend the meeting of the NSAs from BRICS - Brazil, Russia, India, China and South Africa. He is expected to discuss the issue with his Chinese counterpart Yang Jiechi.
Tensions between the two countries escalated as China denied Indian pilgrims entry for the Kailash Mansarovar Yatra through the Nathu La pass in Sikkim.
Beijing initially said it stopped the Yatra due to damage to roads in Tibet after rains and landslides. But soon signalled the matter was related to the standoff between the two armies near Sikkim.
Asked about the statement by the Indian Ministry of External Affairs on Friday that the construction of the road would represent a significant change of status quo with "serious" security implications for India, the Chinese official said they have "noted" the statement by India.
"(The statement) evaded the 1890 convention between Great Britain and China relating to Sikkim and Tibet. But it is this convention which has confirmed the alignment of the boundary between the two sides at the Sikkim section. This convention has been recognised by successive Chinese and Indian governments and has been confirmed by the Indian governments in written form," he said.
"Prime Minister Jawaharlal Nehru has affirmed in his letters to Premier Zhou Enlai, that the convention must be observed. That is the basic principle of international law. It is an obligation that must be fulfilled by the Indian side," he said.
The Chinese official cited two letters Nehru wrote to Zhou - first on March 22, 1959, and on September 26, 1959 - to say that the border between Sikkim and Tibet China is defined by the 1890 Convention and demarcated on the ground in 1895.
"There is no dispute on the border between Sikkim and Tibet," he said, adding that the "trespass" by Indian troops happened at the "defined" Sikkim section. "This is different from frictions and confrontations between the two sides at undefined boundary," Geng said.
China also accused India of using Bhutan as a cover, but evaded questions on Bhutan's protest against the construction of the road, saying the area is Bhutanese territory.
"In order to cover up the illegal entry of the Indian border troops, to distort the fact and even at the expense of Bhutan's independence and sovereignty, they try to confuse right from wrong, that is futile," the Chinese official said.
"We have no objection to normal bilateral relations between India and Bhutan but firmly opposed to Indian side infringing up Chinese territory using Bhutan as an excuse. The Bhutan side does not know previously that the Indian troops entered into the Doklam area, which is not in line with what is claimed by the Indian side," he said.
Geng also claimed that Bhutan "did not know that Indian border troops had entered into the Doklam area which is not in line with what has been claimed by the Indian side."
"We will work with Bhutan without interference of any external forces in maintaining peace and tranquillity of border area and resolving the boundary question," he said.
Bhutan has no diplomatic ties with China. It is supported militarily and diplomatically by India.
Defence experts believe China wants to exert its dominance over the Chumbi Valley, which is a part of the southern reaches of Tibet. By claiming the Doka La area, Beijing wants to maximise its geographical advantage so that it can monitor all movements along the India-Bhutan border.
The Indian Army, meanwhile, has denied that the Chinese army used bulldozers to destroy bunkers in the Sikkim sector last week.
The army also denied that the border standoff with China is the longest ever since 1962.
"The incident is not the longest standoff between the two nations," said a statement issued by the Army spokesman here.