NEW DELHI (Reuters) - India has rejected an Australian request to take part in joint naval exercises with the United States and Japan for fear of antagonizing China, which has warned against expanding the drills, navy officials and diplomats said.

FILE PHOTO: An E-2D Hawkeye plane approaches to the U.S. aircraft carrier John C. Stennis during joint military exercise called Malabar, with the United States, Japan and India participating, off Japan's southernmost island of Okinawa, Japan June 15, 2016. REUTERS/Nobuhiro Kubo/File Photo

Australia formally wrote to the Indian defense ministry in January asking if it could send naval ships to join the July wargames as an observer, in what military experts saw as a step toward eventual full participation.

Four officials from India, Australia and Japan told Reuters India blocked the proposal and suggested that Canberra send officers to watch the exercises in the Bay of Bengal from the decks of the three participating countries’ warships, instead.

New Delhi is worried that China will step up activities in the Indian Ocean where it is building infrastructure in Sri Lanka, Bangladesh and Pakistan, feeding India’s anxiety about being encircled, Indian military sources and diplomats said.

Indian navy officials say there have been at least six submarine deployments by China in the Indian Ocean since 2013 and that Chinese submarines have been docking in Sri Lanka and its long-time ally Pakistan.

“India is being careful about China,” said Abhijit Singh, a former Indian navy officer who heads maritime studies at the Observer Research Foundation in New Delhi.

“India is aware they have upped their maritime engagement in this part of the world and they could just become more brazen with their submarine deployments. We don’t want that to happen,” Singh said.

New Delhi’s ties with Beijing have soured in recent years over a territorial dispute in the Himalayas and China’s military support of Pakistan.

China has also been concerned that Prime Minister Narendra Modi’s avowedly nationalist government has stepped up public engagement of the Dalai Lama, the Tibetan spiritual leader who lives in exile in India and whom it regards as a “splittist”.

An Indian defense ministry spokesman confirmed there had been a request from Australia for observer status in the July exercises, but he said he was not in a position to provide any details of the Indian response.

Both the United States and Japan supported the idea of involving Australia, seeing it as a natural partner in the effort to balance China’s growing might, the four officials said.

MALABAR EXERCISES

The Malabar exercises started out as India-U.S. drills in 1992 but have included Japan every year from 2014.

Dozens of warships, submarines and aircraft take part in the wargames, which are aimed at getting the three powerful navies used to working together. U.S. military officials say this will help in future operations, including joint patrols across the Indian Ocean and the Pacific.

The exercises are now held in waters close to the East and South China Sea as well as the Indian Ocean.

China, which claims most of the South China Sea, has protested the expansion. Neighbors Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims on the strategic waterway, through which about $5 trillion in ship-borne trade passes every year.

A spokesman for Australia’s Minister of Defence Marise Payne refused to comment on the Malabar exercises. But one Australian official, speaking on condition of anonymity because of the sensitivity of the matter, said it was increasingly unlikely Canberra would join the drills although it was keen to do so.

Australia has also traditionally been wary of upsetting China, its largest trading partner.

It takes no sides in the disputes in the South China Sea and has declined to join naval exercises there, although it does support U.S.-led freedom of navigation activities in the region.

Rory Medcalf, head of the National Security College at Australia National University, expressed frustration that China was effectively wielding veto power over other countries’ security cooperation.

India, Japan, the United States and Australia already have bilateral security, dialogue and exercise arrangements with each other, including in some three-country configurations, he said.

“It should be normal and natural for countries with common interests, high levels of trusts and overlapping capabilities to work together on security issues, without another country imposing a veto on who trains with whom,” he said.