Thousands more Marines and sailors will make Australian port calls in coming years as the U.S. boosts it presence in the South Pacific region.

Thousands more More Marines and sailors will patrol the South Pacific asThe Pentagon plans to dispatch part of another three-ship amphibious ready group to the Asia-Pacific region as early as October 2018, Lt. Gen. John Wissler, head of U.S. Marine Corps Forces Command, said on Wednesday. as the U.S. boosts its presence in the volatile region The ships will likely come from the West Coast with an embarked Marine expeditionary unit, he added. 

A Starting in fiscal 2019, an extra Marine expeditionary unit will embark on the Weshead to the be in the Pacific aboard with embarked on West Coast-based ships as early as October 2018, Lt. Gen. John Wissler, head of U.S. Marine Corps Forces Command, said on Wednesday.

The goal is to augment the Marines that currently deploy to Australia's Northern Territory on six-month rotations go to Darwin, Australia, on six month rotations, Wissler said during a discussion at the Center for Strategic and International Studies think tank in Washington, D.C. About 1,250 Marines currently deploy to Australia each year, but U.S. and Aussie officials hope to boost that number to 2,500 by 2020.

Adding another ARG/MEU will mean another 4,000 sailors and Marines will be rotating through the South Pacific.

"The actual basing ... of that and all of those significant details are being worked out," Wissler said. "That’s why it’s a [fiscal] 2019 problem because, as you can imagine, it’s a very complex undertaking." he said.

The Marine Corps has not determined whether the new MEU will come from the continental U.S. United States, Hawaii, or Japan or the Unit Deployment program, Wissler said. U.S. Pacific Fleet could not be immediately reached for comment about the plans.

A spokesman for U.S. Pacific Fleet said it is too soon to say which ships may be assigned to the MEU in fiscal 2019.

"The U.S. Navy remains committed to posturing our most advanced and capable ships and aircraft to the Indo-Asia-Pacific," said Lt. Cmdr. Matt Knight.  "We continually monitor force readiness and capabilities to provide the most robust, capable maritime force possible. Long range planners constantly evaluate whether ships, aircraft, facilities, and equipment are being used effectively and efficiently."

The ARG/MEU would be the second in the Asia-Pacific region, though. The Japan-based 31st Marine Expeditionary Unit currently conducts two 90-day patrols in the Pacific each year: one in the spring and another in the fall. The Marines and sailors also respond to humanitarian crises in the region throughout the year. 

Wissler said the new arrangement would allow that unit to focus on Northeastern Asia while the new ARG/MEU conducted two 90-day patrols in the South Pacific.

About Currently, 1,250 Marines currently deploy to Darwin, Australia each year's Northern Territory each year, but U.S. and Aussie are part of the Darwin rotation and Australian defense officials hope to bump that number up to about 2,500 that a full a Marine air-ground task force rotates to the country annually starting in 2020. That would place a full Marine air-ground task force Down Under.

Wissler did not say which ships would make up the amphibious ready group, but former Chief of Naval Operations Adm. John Greenert has said the amphibious assault ship America is a "prime candidate" to visit Australia as part of such a group.

"They will go into Darwin … and conduct on-load and off-load," Greenert told Navy Times in March 2015 4.

While the Marines train in Australia, the ships in the ARG amphibious ready group can operate and conduct exercises in the Southeast Asia region, Greenert said.

The amount of time Marines can train in Australia is limited by the monsoon season from November to March, during with most of the training center in Darwin is swamped.

"With the way the rainy season works, it is only good to operate around there about six months out of the year," Greenert told Navy Times. "In fact, when we were in Australia, we chose the rainy period. We [now] know what they mean."

The bad weather also makes it difficult for ships like America to offload equipment in Darwin's port, which will need to be expanded to accommodate an amphibious assault ship and two dock landing ships.