In rare condolence to the military chief of another country, emblematic of the growing security partnership between the two nations, US Defence Secretary Lloyd Austin hailed General Bipin Rawat's role in the transformation of India's military and said he had left an “indelible mark” on their defence ties.

“General Rawat left an indelible mark on the course of the US-India defense partnership and was at the center of the Indian Armed Forces’ transformation into a more jointly integrated warfighting organisation,” Austin said in a condolence message. “I and the [Defence] Department extend our deepest condolences to the Rawat family, the Indian military, and the people of India after the tragic passing of Chief of Defense Staff General Bipin Rawat in a helicopter crash,” he said.

Rawat, India's first Chief of Defense Staff, his wife and 11 other Indian Army personnel were killed when their helicopter crashed in the Nilgris on Wednesday.

“I had the privilege of meeting with him earlier this year and viewed him as a valued partner and friend of the United States,” Austin said.

Rawat had visited the US in September and met with Austin, Chairman of Chiefs of Defence Staff General Mark Milley and other officials and visted Joint Base Lewis-McChord in Washington State.

After their meeting, Austin tweeted, “We reaffirmed our enduring commitment to a Free and Open Indo-Pacific and discussed ways to drive greater interoperability between the US and Indian armed forces.”

The US Embassy in New Delhi said that “Rawat spearheaded a historic period of transformation in the Indian military.”

“He was a strong friend and partner of the United States, overseeing a major expansion of India’s defense cooperation with the US military,” it said.