SYDNEY, July 27 (Reuters) - Australia said on Saturday it had signed a A$2.2 billion ($1.4 billion) four-year contract with state-owned submarine builder ASC to upgrade the navy’s Collins class submarines.

The “sustainment contract” is part of a government pledge to keep the diesel-electric powered Collins-class fleet “a potent strike and deterrence capability”, Defence Industry Minister Pat Conroy said in a statement.

The contract will be “directly ensuring job security for more than 1,100 highly skilled workers”, with the work carried out in the towns of Henderson in Western Australia and Osborne in South Australia, Conroy said.