SYDNEY (Reuters) - Australia said on Wednesday it would invest billions of dollars over the next two decades to expand a shipyard in Western Australia that would become the maintenance hub for its nuclear-powered AUKUS submarine fleet.

The government will make an initial investment of A$127 million ($85 million) over three years to upgrade facilities at the Henderson shipyard near Perth, Defence Minister Richard Marles said in a statement.

"The Defence Precinct at Henderson will optimise Australia's shipbuilding and sustainment industry while supporting continuous naval shipbuilding in Western Australia and Australia's nuclear-powered submarine pathway," Marles said.

The facility will also build the new landing craft for the Australian army and the new general-purpose frigates for the navy, he said.

The AUKUS defence pact signed in 2021 between Australia, Britain and the U.S. will see Australia buy up to five nuclear-powered submarines from Washington in the early 2030s before jointly building and operating a new class, SSN-AUKUS, with Britain, roughly a decade later.

AUKUS will be the first time Washington has shared nuclear-propulsion technology since it did so with Britain in the 1950s though the submarines would not be nuclear armed. The deal is expected to cost Australia up to about A$368 billion ($245.8 billion) by 2055, according to government estimates.

($1 = 1.4975 Australian dollars)

(Reporting by Renju Jose in Sydney; Editing by Raju Gopalakrishnan)