Australia and the United States launched their biggest joint war games Monday, with 27,500 troops backed by a US aircraft carrier engaging in exercises aimed at consolidating the allies' military dominance in the Asia Pacific region. The biennial Talisman Sabre exercise pits 20,000 US troops and 7,500 Australian forces against two fictional enemies - the Kamarians and Musorians - in a variety of land and sea-based scenarios designed to test their skills in combat, peacekeeping and humanitarian relief efforts. The exercise, which runs until July 2, will also include 10 US ships, 20 Australian ships and 125 aircraft operating off the coast of Rockhampton in northeastern Queensland state. "The United States and Australia have a long-standing relationship ... we share the same values and interests. Foremost among those interests is the stability and security of the Asia-Pacific region," US Vice Admiral Doug Crowder told reporters on board the USS Blue Ridge in Sydney. "Therefore it is very important that our militaries train together to carry out the types of missions our governments may call upon us to execute to ensure regional security and stability." The exercise comes as the United States and Japan step up efforts to build a joint missile defense system in Asia, partly as a bulwark against regional threats such as a nuclear-armed North Korea. Australia, a steadfast US ally that maintains around 2,000 troops in Afghanistan and Iraq, is studying whether to participate in the defense shield, Defense Minister Brendan Nelson announced this month. Canberra is expanding its military personnel to 30,500 troops from 27,500, and ramping up other defense capabilities as part of an overhaul to take greater responsibility for Asian security. Japan plans to send observers to the Talisman Sabre operation, Crowder said, but would not expand on what role they might play in the exercise. Australia and Japan signed a security agreement in March that will enable Japanese forces to train alongside Australians for disaster relief and peacekeeping missions, and boost cooperation between the two countries in counterterrorism measures and intelligence sharing. Meanwhile, environmentalists have voiced concern about the possible dangers of submarine-hunting sonar equipment to whales in the region. The International Whaling Commission issued a report this month saying a mid-frequency sonar sometimes used by US and Australian ships can cause hearing loss and tissue damage in whales and can alter their diving habits. "A huge part of the planning for this exercise has been the environmental concerns. We have many procedures in place," Crowder said. He would not elaborate on the procedures, saying only that the operation "will be conducted in compliance with all the Australian governmental requirements." About 100 people gathered Monday outside an army barracks in the northeastern city of Rockhampton to protest the exercises. They laid a wreath and hundreds of shoes at the gate of the barracks to symbolize military and civilian casualties from the Iraq war. "We mourn all loss of life and we feel the shoes are a very powerful symbol," Robin Taubenfeld, of the environmental group Friends of the Earth said.