India condemned a new road that China is building on the rivals' Himalayan border on Friday, saying it raises "serious security" concerns.
The two sides are trading increasingly stern diplomatic warnings over the new hotspot, a remote scrap of territory where the frontiers of China, India and Bhutan meet.
Beijing made a formal protest this week, accusing Indian border guards of crossing from the northeastern state of Sikkim into its Tibetan territory to stop the road building.
India's foreign ministry said Friday that China's People's Liberation Army (PLA) troops entered the area to "unilaterally" construct the road.
"India is deeply concerned at the recent Chinese actions and has conveyed to the Chinese government that such construction would represent a significant change of status quo with serious security implications for India," a ministry statement said.
"India cherishes peace and tranquillity in the India-China border areas. It has not come easily," it said, urging Beijing to resolve the skirmish through dialogue.
India and China have long disputed parts of their Himalayan border, and regularly accuse each other of making illegal troop encroachments.
Bhutan has also lodged a formal protest to China, saying the road violated a bilateral agreement.
Bhutan, which does not have diplomatic relations with China, still disputes sovereignty of the land. And the showdown is part of a wider friction between India and China over the 4,057 kilometer (2,520 mile) border.