WASHINGTON, March 8 (Reuters) - Australia is expected to buy up to five U.S. Virginia class nuclear powered submarines in the 2030's as part of a landmark defense agreement between Washington, Canberra and London, four U.S. officials said on Wednesday, in a deal that would present a new challenge to China.

The agreement, known as the AUKUS pact, will have multiple stages with at least one U.S. submarine visiting Australian ports in the coming years and end in the late 2030's with a new class of submarines being built with British designs and American technology, one of the officials said.

U.S. President Joe Biden will host leaders of Australia and Britain in San Diego on Monday to chart a way forward for provision of the nuclear-powered submarines and other high-tech weaponry to Australia.

China has condemned the effort by the Western allies, who are seeking to counter China's military buildup, pressure on Taiwan and increasingly muscular deployments in the contested South China Sea.

Two of the officials, speaking on the condition of anonymity, said that after the annual port visits, the United States would forward deploy some submarines in Western Australia by around 2027.

In the early 2030's, Australia would buy 3 Virginia class submarines and have the option to buy two more.

AUKUS is expected to be Australia's biggest-ever defense project and offers the prospect of jobs in all three countries.

Australia has an existing fleet of six conventionally powered Collins-class submarines, which will have their service life extended to 2036. Nuclear submarines can stay underwater for longer than conventional ones and are harder to detect.

The officials did not elaborate on the planned new class of submarines, including offering specifics about production locations.

The Pentagon referred queries to the White House, which declined to confirm details about any upcoming announcement. The British Embassy in Washington did not comment directly on the Reuters report but repeated an announcement from London that British Prime Minister Rishi Sunak would travel to the United States for further talks on AUKUS.

The Australian Embassy in Washington did not immediately respond to a request for comment.

Under the initial AUKUS deal announced in 2021, the United States and Britain agreed to provide Australia with the technology and capability to deploy nuclear-powered submarines as part of joint efforts to counter the increasing threat posed by China in the Indo-Pacific region.

But a deal between the three countries on how specifically to achieve that goal had not been ironed out.

The U.S. Congress has been briefed several times in recent weeks on the impending AUKUS deal to garner support for the legal changes needed to smooth out technology transfer issues for the highly protected nuclear propulsion and sonar systems that will be aboard Australia’s new submarines, a congressional source said.

Over the next five years, Australian workers will come to U.S. submarine shipyards to observe and train. This training will directly benefit U.S. submarine production as there is currently a labor shortfall for shipyard workers the U.S. needs to build its submarines, the source said.

It is unclear how the upcoming announcement might affect the U.S. Navy's expectations for its own submarine acquisitions in coming years.

The Navy’s 30-year shipbuilding plan released last year forecast submarines being produced at a rate of 1.76 to 2.24 per year and forecast the fleet grow to between 60 to 69 nuclear attack submarines by 2052, according to the Congressional Research Service.

General Dynamics Corp (GD.N), which makes Virginia class submarines, has 17 of them in its current backlog delivering through 2032.

To date no party to the nuclear Non-Proliferation Treaty (NPT) other than the five countries the treaty recognizes as weapons states - the United States, Russia, China, Britain and France - has nuclear submarines.