NEW DELHI: India and the US are planning to further upgrade their already expansive and top-level Malabar annual naval exercise , in which Japan has now become a regular participant , with a renewed thrust on anti-submarine warfare operations.This comes at a time when the Indian security establishment in keeping a close watch on the increasing forays by Chinese nuclear and conventional submarines in the Indian Ocean Region (IOR).The Indian Navy has tracked at least six Chinese submarines in the IOR, with an operational turn-around stop mainly at Karachi, over the last four years, as was earlier reported by TOI.After meeting Navy chief Admiral Sunil Lanba and other top officials here on Friday , the commander of the US Seventh Fleet Vice Admiral Joseph P Aucoin said, “We want to make the 21st Malabar exercise , which will be held in the IOR next year, bigger and more complex.“Noting that the Indian Navy now also operates the P-8I Poseidon long-range maritime patrol aircraft, a variant of the US Navy's P-8As, Vice Admiral Aucoin said the two sides “can hunt submarines together“ as part of the several missions undertaken during the Malabar exercise.“Anti-submarine warfare (ASW) is one area I think would be very beneficial. So, I am looking forward to it in the Malabar,“ he said.India is extensively using its P-8I aircraft, which are packed with radars and armed with deadly Harpoon Block-II missiles, MK-54 lightweight torpedoes, rockets and depth charges, to keep tabs on Chinese submarines in the IOR.The US, of course, would like to include other countries like Australia in the Malabar wargames on a regular basis to build interoperability in the Asia-Pacific region. But China views any such “naval grouping“ as a move to contain it, and had lodged a strong protest against the Malabar exercise in the Bay of Bengal in 2007 when it had been expanded to include Japan, Australia and Singapore.The UPA government had then restricted the Malabar to just a bilateral endeavour with the US whenever it was held near Indian waters. Japan was included only when the exercise was held in north-western Pacific in 2009 and 2014. But after it came to office in 2014, the NDA government has made Japan a permanent fixture in the Malabar series. Japan took part in the exercise held in Bay of Bengal in October 2015 as well as in the western Pacific in June this year.Vice Admiral Aucoin, on his part, said that while he felt that “multi-lateral exercises“ were “very good“ to build interoperability in the Asia-Pacific, it was up to the Indian and US governments to take a call on whether the Malabar should be expanded to include other countries as well. “I am happy at the way Malabar has become a tri-lateral, with the navies of three democracies working closely together,“ he said.India has been cranking up the strategic partnerships with both US and Japan, with maritime cooperation emerging as a major thrust area.With the US a new bilateral maritime security dialogue as well as navy-to-navy talks on anti-submarine warfare have been set in motion now.