A sea-based missile defense test flight will take place today off Kaua'i amid reports North Korea may be prepping to test-fire a long-range missile over the Pacific.

The director of the Missile Defense Agency, Air Force Lt. Gen. Henry "Trey" Obering, was scheduled to view the test flight on Kaua'i, but the trip to Hawai'i was canceled "due to current events," Missile Defense Agency spokesman Chris Taylor said.

The Kaua'i test is part of the Aegis Ballistic Missile Defense Program and had been scheduled for months and was not related to any developments in North Korea, Taylor said. But reports of a possible test launch by the reclusive nation have focused new attention on the U.S. missile defense effort and given new impetus to the large-scale "Valiant Shield" war games involving three U.S. aircraft carriers under way off Guam.

The ship-based test for short- and medium-range ballistic missile intercepts involves the Pearl Harbor-based USS Lake Erie, one of three cruisers capable of shooting down ballistic missiles.

A target will be launched from the Pacific Missile Range Facility at Barking Sands, and the cruiser USS Shiloh out of San Diego will detect and track the target with its SPY-1B radar and fire an SM-3 missile to intercept it.

The Aegis weapon system will guide the SM-3 missile through its first, second and third stages, and the release of a warhead to intercept the target's re-entry vehicle.

The test will gauge the ability to intercept a medium-range separating ballistic missile in its midcourse phase of flight. The test is the eighth intercept flight test attempt. Six of the previous seven flight tests resulted in successful intercepts, the Missile Defense Agency said.

Four U.S. destroyers, along with a modified Japan Maritime Self Defense Force ship, will take part in test activities including long-range surveillance and tracking. It's the first time an allied military has participated in an Aegis ballistic missile defense test.

Ground-based interceptor missiles in Alaska and California could be used to counter the long-range Taepodong-2 missile North Korea is said to be readying, but the $91 billion missile defense system still is in testing.

The Washington Post reported that the U.S. destroyers Curtis Wilbur and Fitzgerald, both out of Yokosuka, Japan, were operating off the North Korean coast yesterday. The ships feature sensors that would swiftly detect and track a missile's flight.

The Pearl Harbor cruisers Lake Erie and Port Royal — along with the Shiloh — have the ability to track and shoot down ballistic missiles. The Port Royal is in the Arabian Gulf, the Navy said.

Jon Yoshishige, a U.S. Pacific Fleet spokesman, said the Navy has a guided missile destroyer deployed on a virtually continuous basis in the Sea of Japan to serve as a long-range surveillance and tracking platform as part of the U.S. missile defense system.

Fifteen destroyers have long-range surveillance and tracking capability, and beginning this year, the U.S. will begin to install the ballistic missile engagement capability as well, an official said.

An agreement is in place with Japan for the next iteration of the SM-3 missile that has more thrust capability and might bring sea-based inter-continental ballistic missile shoot-down capability, "but right now, the ICBM capability is in the interceptors that are in (Alaska and California)," Taylor said.

Those interceptors have less of a record of success, with five test intercepts out of eight attempts since 1999, Taylor said.

The Navy also is making a point of demonstrating its carrier strength in the Pacific.

The carriers Reagan, Lincoln and Kitty Hawk are operating near Guam for the "Valiant Shield" military exercise through Friday. The Lincoln will take part in upcoming Rim of the Pacific war games off Hawai'i, and the Lincoln and another carrier will train in the western Pacific in August, the Navy said.

The Guam exercise represents the largest gathering of flattops for an exercise in the Pacific in more than a decade, if not longer, officials said. The force participating involves approximately 22,000 U.S. military personnel, 30 ships and 280 aircraft, he said.

U.S. Pacific Command said assembling three carriers and their supporting ships, submarines, supporting air wings and other air and land elements "demonstrate the U.S. military's ability to conduct robust joint command and control operations."

The Navy wants to be able to dispatch more carriers on shorter notice as North Korea remains a threat and China builds up its military.

Reach William Cole at wcole@honoluluadvertiser.com.