By almost any standard, the white ship with a red cross on its bow that sailed out of Pearl Harbor yesterday afternoon is gargantuan.

Long as three football fields, the USNS Mercy is a floating medical center fashioned from a converted supertanker. It's equipped with a dozen operating rooms, a total patient capacity of 1,000 beds, and room for 1,300 staff and crew.

For its four-month Pacific Partnership 2008 mission that began yesterday, the Mercy's capacity has been trimmed to a crew of 500 (including 50 physicians), around 100 beds, three operating rooms, one emergency room, a four-bed intensive care unit and an isolation ward.

Once the ship reaches Guam, the crew will expand to around 800, said ship Capt. Robert Wiley.

"Mercy is a fully functioning, fully equipped, fully staffed hospital that we can take just about anywhere in the world anytime it's needed," said Wiley. "One of the most remarkable things about the Mercy is how it allows so many different organizations and groups to come together and work. I think that's the theme of this mission — civic partnership."

Commodore Bill Kearns has been assigned as mission commander for the multinational humanitarian assistance operation, which he said will take the ship to the Philippines, Vietnam, Timor-Leste, Papua New Guinea and Micronesia.

"We'll be working very closely with those countries, plus the relief agencies that are already in those countries," Kearns said. "Our work will complement their work. We want to help out those countries in medically underserved regions. We want to show that we're a Pacific nation, and that we want to be a good neighbor."

A team from Hawai'i-based Aloha Medical Mission is among the relief organizations supporting the USNS Mercy's mission.

Mercy prides itself on being able to adjust quickly to any situation. And with the eyes of the world focused on the tens of thousands of cyclone victims in Myanmar, Kearns said it would be no problem to go there if asked. So far the Myanmar government has not asked, and Mercy has not been assigned to go there.

"As of now our mission is to go out and execute Pacific Partnership 2008," Kearns said. "But, if called upon, we have the flexibility to assist (cyclone victims in Myanmar)."

To prepare for its Pacific Partnership mission, site survey teams were sent to the host countries in advance to coordinate with ministries of health, embassies and various agencies to identify what's needed to assist those countries.

Mercy is then staffed and equipped to meet the requirements of the host nations. Upon arrival, Mercy performs both sea- and shore-based missions. Its sea-based surgery, lab, radiology and pharmacy capabilities are augmented by its shore-based primary care, internal medicine, dental care, preventive medicine and even veterinary care aspects.

The story of Mercy's unique mission was formulated after the ship was called on to assist in the tsunami disaster of 2004.

The primary mission of Mercy was and still is to provide rapid combat casualty care to Army, Navy, Air Force and Marine forces around the world. But part of Mercy's secondary mission hadn't been fully realized until the tsunami disaster struck.

"This ship has two other missions, and those are humanitarian assistance and disaster relief," explained Capt. James Rice, who heads Mercy's Medical Treatment Facility. For the past four years, Mercy has expanded on its humanitarian and relief roles.

"So we will arrive at the invitation of the host nation to provide what services they would like from us. And what we can provide is state-of-the-art care that you could receive at any hospital here in Hawai'i."

Pacific Partnership 2008 is a humanitarian civic assistance mission, Rice said. If Mercy were called upon to go to Myanmar, that would be an example of the ship's disaster relief mission.

The key to the ship's special role is its flexibility and rapid response capability, Rice said.

"The USNS Mercy is ready to deploy to any assignment that our government needs us to perform," he said.