NEW DELHI, May 24 (Reuters) - India faces a greater threat from China than Pakistan because New Delhi knows little about Beijing's combat capabilities, India's air force chief told a newspaper in an interview published on Sunday.

The world's two most populous nations fought a brief but brutal war over their 3,500 km (2,200 mile) Himalayan border in 1962, and both sides claim the other is occupying big but largely uninhabited chunks of their territory.

India has also been pursuing closer relations with the United States, something that worries China.

China has a standing army almost three times the size of Pakistan's, according to official figures and defence industry estimates, but it is the lack of knowledge about China's military that concerned Air Chief Marshal Fali Homi Major. "We know very little about the actual capabilities of China, their combat edge or how professional their military is," Major told the Hindustan Times newspaper.

"They are certainly a greater threat."

India and Pakistan have fought three wars since independence in 1947 and tensions between the nuclear-armed neighbours rose sharply after last November's Mumbai attack, which killed 166 people. A slow-moving peace process was paused after the attack.

Islamabad has acknowledged that the attack was launched from and partly planned in Pakistan, but rejected New Delhi's accusations that the gunmen had support from official Pakistani agencies.

Although India and China have signed a treaty to maintain "peace and tranquility" along their disputed frontier and agreed to find a political solution to the row, talks have hardly made progress even as their business ties boom.

India blames the lack of progress on China's claim over the northeastern state of Arunachal Pradesh, in particular over its Buddhist enclave of Tawang. New Delhi says it cannot part with populated areas to settle the border dispute.

Major said the Indian air force was upgrading about five airbases, of which two would operate Russian Su-30 MKI fighters. (Reporting by Krittivas Mukherjee; Editing by Paul Tait)

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