Irene Hirano Inouye, the widow of U.S. Sen. Dan Inouye, will participate in a keel-joining ceremony — a major milestone in the life of a Navy ship — in May in Bath, Maine, as work progresses on the $1.5 billion destroyer named for the Medal of Honor recipient and legendary Hawaii lawmaker.

Delivery of the USS Daniel Inouye has slipped more than a year due to a schedule change with the contractor, which means the 510-foot warship won’t arrive in Hawaii until 2020.

Inouye said she was grateful and humbled to be asked to be the ship’s “sponsor.” The keel ceremony is scheduled for May 14.

The naming of the ship for the senator “is really a wonderful tribute,” Inouye said in a phone interview. “It’s something that I know he would be extremely proud of. He would also feel it was a tribute to those that he served with in the military and for the sacrifices that they made.”

In 2013 then-Navy Secretary Ray Mabus announced that a new destroyer would be named after Sen. Inouye, whom he called “a true American hero.”

Inouye, part of the fabled Japanese-American 442nd Regimental Combat Team, lost his right arm attacking multiple German machine gun positions in Italy in 1945, and later received the Medal of Honor.

He went on to become one of the most powerful members of the U.S. Senate. He died in late 2012.

The USS Daniel Inouye is expected to be commissioned in Hawaii in 2020 at what will be a major event. More than 2,000 people attended the July Pearl Harbor commissioning of a destroyer named after Dec. 7, 1941, hero Chief John Finn, who fired back at attacking planes even after receiving 21 shrapnel and bullet wounds.

The Navy said the USS Daniel Inouye’s completion has been delayed so the shipyard where it is being built can also work on other vessels.

Shipbuilder General Dynamics Bath Iron Works started fabrication on the USS Daniel Inouye in October 2014. The vessel was originally expected to be delivered to the Navy late this year.

But the construction schedule — the warship is 44 percent complete, according to the Navy — was modified in part due to the complexity of another type of destroyer being built by Bath.

The Maine shipyard is producing three Zumwalt- class destroyers — futuristic-looking stealth ships with a wave-piercing “tumblehome” hull.

The Zumwalts, at 610 feet, are much bigger than the USS Daniel Inouye, which is an Arleigh Burke-class guided-missile destroyer. The Zumwalts were envisioned to replace the Arleigh Burkes, which were first put into service in 1991.

Up to 32 of the Zumwalts — designed to provide land-pounding firepower akin to old battleships from the littorals, or near-shore waters — were to be built.

But with costs spiraling and a shift in focus to “great power” competition with China and Russia, production was halted on the now more than $4 billion Zumwalts at three, and construction was restarted on upgraded Arleigh Burke destroyers.

Bath Iron Works has been responsible for the new ship class — the Zumwalts — while also building Arleigh Burke destroyers. Huntington Ingalls Industries in Pascagoula, Miss., is also building Arleigh Burke destroyers.

Capt. Casey Moton, the Arleigh Burke program manager, said in an email that “in late 2016, the Navy and Bath Iron Works mutually agreed on ship schedule adjustments” for Bath to more efficiently sequence their ship construction efforts for the Zumwalt class and the restart of the Arleigh Burke class production line.

As a result, the delivery date for the USS Daniel Inouye was changed from December of this year to April 2020, Moton said.

The keel-laying ceremony in May will reflect the joining of two major sections of the ship. Launch is planned by early 2019, the Navy said.

Arleigh Burke destroyers are multimission ships equipped with the Aegis combat system, an integrated ship combat system named for the mythological shield that defended Zeus, according to the Congressional Research Service. Some of the destroyers have ballistic missile shoot-down capability.

The Navy previously said the “technology insertion” destroyers such as the USS Daniel Inouye would include “better onboard power-generation systems, increased automation and next-generation weapons, sensors and electronics.”