For more than a month, Indian and Chinese troops have been locked in a standoff on a remote but strategically important Himalayan plateau near where Tibet, India and Bhutan meet

China has stepped up its rhetoric in an increasingly tense border row with India, hinting at the possibility of military action in a propaganda push that analysts are calling "genuinely troubling."

For more than a month, Indian and Chinese troops have been locked in a standoff on a remote but strategically important Himalayan plateau near where Tibet, India and Bhutan meet.

On Thursday, Chinese defence ministry spokesman Ren Guoqiang warned that Beijing had shown restraint but had a "bottom line."

"No country should underestimate the Chinese forces'... resolve and willpower to defend national sovereignty," he said in a post on the ministry website.

It is a line that has been echoed almost word for word this week by the foreign ministry, the official Xinhua news agency, the ruling Communist Party mouthpiece the People's Daily, the official military news website of the Chinese armed forces, and other outlets.

On Wednesday, the foreign ministry released a 15-page document of "facts" about the border dispute, which included a map of alleged intrusions and photographs of what it stated were Indian troops and military vehicles on China's side of the frontier.

Calling for the "immediate and unconditional" withdrawal of Indian troops, it warned Beijing would "take all necessary measures" to safeguard its interests.

Chinese foreign ministry spokesman Geng Shuang said Thursday that India was building roads, hoarding supplies and deploying a large number of troops in the area.

"This is by no means for peace," Geng said.

- 'Genuinely troubling' -

Mistrust between the giant neighbours goes back centuries and the pair fought a brief war in 1962 in India's border state of Arunachal Pradesh.

The recent escalation of China's rhetoric was "genuinely troubling," Rory Medcalf, head of Australian National University's National Security College, told AFP.

"It suggests that diplomatic conversations, including among high-level national security advisers, are failing to find a face-saving way for the two powers to withdraw their forces," he said.

The plateau is strategically significant as it gives China access to the so-called "chicken neck" -- a thin strip of land connecting India's northeastern states with the rest of the country.

Despite the heated war of words, other analysts played down the possibility of an armed clash.

"The point of these statements isn't that war is imminent; rather, they're an attempt to figure out how to not go to war without losing face," Shen Dingli, vice dean of Fudan University's Institute of International Studies, told AFP.

"Neither side wants to go to war, but China and India are acting like two unhappy little children."

China has rolled out a massive new global infrastructure programme known as the "One Belt, One Road" initiative, which it presents as a peaceful development policy to connect Chinese companies to new markets around the world.

Critics see it as a geopolitical powerplay.

President Xi Jinping is set to meet Indian Prime Minister Narendra Modi at a summit of BRICS nations in the Chinese city of Xiamen in early September and has said he hopes for greater cooperation within the bloc.

But he is also gearing up for a key party congress later this year, at which he is expected to further consolidate his grip on power -- making him unwilling to appear weak by backing down in the current dispute, said politics professor Yvonne Chiu, who researches China's military at Hong Kong University.

Chiu said China was testing "how much they can get away with, in a region that is unlikely to draw the involvement of other major powers such as the US."