A U.S. missile defense test that an official said was delayed off Kauai earlier this week due to the presence of a Russian surveillance ship was carried out today with a salvo of SM-6 ship-fired missiles failing to intercept a medium-range ballistic missile target.

The Missile Defense Agency, in cooperation with the U.S. Navy, said it conducted what it called Flight Test Aegis Weapon System 31.

“The objective of the test was to demonstrate the capability of ballistic missile defense (BMD)-configured Aegis ship to detect, track, engage and intercept a medium-range ballistic missile target with a salvo of two Standard Missile-6 Dual II (BMD-initialized) missiles. However, an intercept was not achieved,” the agency said in a news release.

Program officials have initiated an “extensive review” to determine the cause of any problems which may have prevented a successful intercept, the agency added.

A Russian spy ship loitering in international waters off Kauai for several days had delayed the missile test, an official said Wednesday.

>> RELATED: Russian spy ship off Kauai results in postponed missile test

U.S. Pacific Fleet at Pearl Harbor said in a statement at the time that it was “aware of the Russian vessel operating in international waters in the vicinity of Hawaii, and will continue to track it through the duration of its time here. Through maritime patrol aircraft, surface ships and joint capabilities, we can closely monitor all vessels in the Indo-Pacific area of operations.”

An official previously said the test was delayed because the United States did not want the Russian vessel to “collect on” the effort.

The Missile Defense Agency said today that, “We executed this test within the test window so there was no delay.” It was not immediately clear if the Russian ship had departed the Hawaiian islands.

U.S. Naval Institute News, which was the first to report the presence of the ship, said it was the Russian Navy Vishnya-class auxiliary general intelligence, or AGI, ship Kareliya (SSV-535).

The Vladivostok-based ship is one of seven AGIs specializing in signals intelligence, USNI News said.

The website navyrecognition.com reported in 2017 that the Kareliya had been mothballed for more than 10 years until January 2014 when a “comprehensive repair and retrofit of the ship” was performed. After that, it was turned over to the Russian Pacific Fleet.

USNI News said the Russian ship was operating 13 nautical miles west of Kauai in international waters. Territorial waters begin at 12 nautical miles.

“Russia is testing hypersonic weapons and maybe seeking insights into our missile systems that might enhance their hypersonic weapons ability to penetrate our defenses,” said retired Navy Capt. Carl Schuster, a former director of operations at U.S. Pacific Command’s Joint Intelligence Center and an adjunct professor at Hawaii Pacific University.

He added that the missile defense test “is an intelligence opportunity that is hard to ignore.”

Riki Ellison, chairman of the nonprofit Missile Defense Advocacy Alliance, said the test may have been focused on the emerging hypersonic threat — increasing the interest of Russia.

“The planned test could be leveraging the vast (Pacific) range for testing United States capability on hypersonic missiles that Russia and China are competing with the United States on,” Ellison said.

If the target missile replicated characteristics of a hypersonic missile, it may have been harder to hit.

The Missile Defense Agency did not announce ahead of time that a test would be conducted off Kauai. The agency routinely reveals after the fact the results of missile defense tests, which typically cost many millions of dollars and involve hundreds of personnel.