Two US aircraft carriers staged a rare show of force in the South China Sea yesterday in what was seen as a response to large-scale PLA exercises in the Taiwan Strait. The USS Carl Vinson, the USS Constellation and their battle groups - believed to comprise another 13 warships and submarines - carried out a one-day exercise in the sea, most of which is claimed by Beijing. The operation involved 15,000 personnel, 130 naval aircraft and 20 US air force aircraft. The USS Constellation and its support ships are due to dock in Hong Kong on Monday. While the US navy officially sought to play down its significance, analysts said the display of American military might was clearly designed to send a message over Taiwan. It also echoed the US decision to send aircraft carriers to waters around Taiwan when the PLA fired missiles in the strait during the island's 1996 presidential elections. 'There are no coincidences around the Taiwan Strait and the Americans would have been fully aware of the PLA's exercises when they planned this,' said Paul Beaver, an independent defence analyst in Britain. 'They are demonstrating to the PLA that they have an interest in the future of Taiwan.' The aircraft carriers held a 'passing exercise', involving the launching of the fighter jets and joint operations between the two battle groups. The mainland military's exercises on and around Dongshan Island in the Taiwan Strait involving tens of thousands of troops, advanced fighters, warships and missiles were launched on Sunday and are expected to run until next week. The exercises have been dubbed one of the PLA's largest war games. They reportedly involve practising 'attacking and occupying an outlying Taiwanese island and fighting off an aircraft carrier'. Any hostile reaction to the exercises held by either nation could harm ties that have been improving since the collision of a US spy plane and a PLA fighter jet in April which killed the Chinese pilot and led to the detention of the US aircraft's crew. Taiwan would be reassured by the US exercise, said military expert Andrew Yang Nien-dzu, secretary-general of the Chinese Council of Advanced Policy Studies in Taipei. 'It's a show of strength, especially after the collision, that they will not stop their military activities in the region,' he said. An official report on the US 7th Fleet's Web page last night described the exercise involving the nuclear-powered USS Carl Vinson and the conventionally powered USS Constellation as a 'rare meeting at sea'. 'Along with the valuable training benefits achieved during the exercise, the meeting of the aircraft carrier battle groups on the high seas demonstrates a commitment to providing peace and co-operation in the region while preserving the right to freedom of navigation,' it said. A 7th Fleet spokesman told the South China Morning Post the air force aircraft and warships joined forces to test complex air traffic control procedures, manoeuvring of ships, command and control functions as well as other procedures. The spokesman said the exercises were not intended to send a 'specific message' to China. 'This exercise was conducted in the South China Sea because that is where the two battle groups passed each other,' he said. Analysts insisted the US exercise sent a strong message. 'It is a very obvious response to the [mainland] exercise,' said Joanna Kidd, naval analyst at the International Institute of Strategic Studies in London. The USS Constellation battle group was returning to San Diego from a six-month deployment to the Arabian Gulf and the USS Carl Vinson was on its way to the Middle East. 'Given the wide-ranging tasking for battle groups, this opportunity to conduct multi-carrier operations rarely presents itself and we have to take advantage of it when we can,' said the spokesman. He declined to pinpoint the exercise's exact location, but said it took place over a 'vast expanse' in what the US describes as 'international waters'. The last time an exercise involving two US aircraft carriers took place in the region was in August 1999 when tensions were high between Beijing and Taipei over former Taiwan president Lee Teng-hui's proposal that relations be conducted on a 'state-to-state' basis.