US President Donald Trump offered Wednesday to mediate in what he called a "raging" border showdown between India and China in the Himalayas.

Trump's offer came after Indian defence sources said hundreds of Chinese troops had moved into a disputed zone along their 3,500 kilometre-long (2,200 mile) frontier. Two weeks ago several Indian and Chinese troops were hurt during fistfights and stone-throwing in another sector. There has been no violence reported since, however.

While blaming each other for the flare-up, the world's two most populous countries have stressed the need to negotiate a settlement to the latest dispute along their tortuous border.

Trump, who has sought closer ties with India in recent years while also being involved in a tense trade showdown with China, made his offer in a Twitter statement. "We have informed both India and China that the United States is ready, willing and able to mediate or arbitrate their now raging border dispute. Thank you!" he said.

Last year Trump offered to mediate between India and Pakistan over their Kashmir dispute, but it was tersely rejected by India.

Alice Wells, the top US State Department official for South Asia, said last week that China was seeking to upset the regional balance and had to be "resisted". India and China fought a war over India's northeastern state of Arunachal Pradesh in 1962. China still claims some 90,000 square kilometres (35,000 square miles) of territory under New Delhi's control.

While no shot has been fired across their border for more than four decades, there have been numerous face-offs. In 2017 there was a 72-day showdown after Chinese forces moved into the disputed Doklam plateau on the China-India-Bhutan border. Punches and stones were thrown this month at Naku La in India's Sikkim state, which borders Bhutan, Nepal and China, before "dialogue and interaction" calmed tempers.

The focus has since moved to India's Ladakh region across the border from Tibet. Indian defence sources say Chinese forces have moved into Indian territory at four points. The sources said hundreds of Chinese troops and vehicles have taken over the Indian side of the Galwan valley, one of the four disputed sites.

Diplomatic and military observers said both sides seemed to be digging in for another long face-off. Their rival foreign ministries have denied any fault but called for established negotiating channels to be used.

India's Prime Minister Narendra Modi and China's President Xi Jinping have sought to ease the tensions at summits over the past two years when they agreed to boost border communications between their militaries