NEW DELHI (Reuters) - India and the United States began a massive joint military exercise on Monday, underscoring their deepening security ties they view as crucial in a troubled South Asia region. Hundreds of soldiers using heavy transport aircraft and battle tanks are participating in the biggest-ever war games between the two countries which were on the opposing side of the Cold War but now seek to build strategic and military ties. This exercise is a clever policy for India, a correct thing to do and is clearly part of a larger programme started by both countries to improve relations by shedding old inhibitions, Naresh Chandra, a former envoy to Washington said. The two countries share security concerns centred around Pakistan and Afghanistan, and New Delhi seeks to enlist American support to press Islamabad to tackle what it calls militants on its soil. They also both share concerns about a rising China. Afghanistan and Pakistan will remain areas of concern for both countries and the US, instead of leaving Afghanistan as a theatre, is looking to quarantine the security threat in the region itself, said Uday Bhaskar, a strategic analyst. Therefore, this tactical exercise between the two countries to prepare their troops for future makes sense, Bhaskar, director of the National Maritime Foundation, said. The military exercise comes after 17 people were killed last week in a bomb attack on the Indian embassy in Kabul that renewed focus on Indias tense relations with Pakistan.