SYDNEY, March 16 (Reuters) - Australian Prime Minister Anthony Albanese on Thursday defended the country's A$368 billion ($244.06 billion) plan to acquire nuclear submarines, after two former leaders criticised the deal over its cost, complexity and potential sovereignty issues.

Unveiled on Tuesday in San Diego, the multi-decade AUKUS project will see Australia purchase U.S. Virginia-class submarines before joint British and Australian production and operation of a new submarine class, SSN-AUKUS.

After criticism from Malcolm Turnbull and Paul Keating, both former prime ministers, Albanese said that the deal was necessary given the buildup of Chinese military power in the region, which he called the largest since World War Two.

"China has changed its posture and its positioning in world affairs since the 1990s... that's the truth of the matter," he said.

Turnbull said on Thursday that the AUKUS project would take longer and cost more than an alternative plan to buy conventional French submarines, "recklessly" scrapped in 2021.

"We've been caught up in this hoopla where anyone who expresses any concerns about it is accused of being or implied they are lacking in patriotism," Turnbull said.

Paul Keating, a former Prime Minister under the ruling Labor Party, on Wednesday called AUKUS the worst foreign policy mistake by the party since a failed bid to introduce conscription in World War One.

Buttressed by bipartisan support in Parliament, criticism of the security pact has been mostly confined to academics, former politicians and minor parties.

Opting for nuclear submarines in the U.S.-Britain alliance over conventional alternatives would leave Australia with fewer submarines while constraining the country's ability to operate independently of the United States, he said.

"Anthony Albanese screwed into place the last shackle in the long chain the United States has laid out to contain China," he said.

Some analysts have argued nuclear submarines are preferable because their superior range and stealth will help protect Australia's trade routes from Chinese aggression.