Washington (CNN) The Pentagon successfully shot down an intercontinental ballistic missile using its own upgraded long-range interceptor missile on Tuesday in what was widely seen as a test of US ability to counter a North Korean missile launch.

The Missile Defense Agency launched a ground-based interceptor from Vandenberg Air Force Base in California to intercept a US-launched mock ICBM target over the Pacific Ocean, according to a US defense official.

The test ICBM, which flew thousands of miles per hour, was destroyed "thousands of miles off the coast" of the US mainland, with the intercept taking place northeast of Hawaii, the director of the Missile Defense Agency, Vice Adm. Jim Syring, told reporters at the Pentagon via a Wednesday phone call.

The interceptor "destroyed the target in a direct collision," according to a statement from the Missile Defense Agency.

"The intercept of a complex, threat-representative ICBM target is an incredible accomplishment ... and a critical milestone for this program," Syring said in a statement shortly after the test.

"This system is vitally important to the defense of our homeland, and this test demonstrates that we have a capable, credible deterrent against a very real threat," he said.

"Everything we did was operationally realistic," Syring told reporters, adding that "decoys" were deployed by the target ICBM to make the test more realistic.

He said that the test ICBM "flew at a higher altitude and a longer range and a higher velocity than any other target we've flown to date."

He said the designers of the test ICBM worked with the intelligence community in order to replicate a realistic Iranian or North Korean threat that the US might face between now and 2020.

"I was confident before the test that we have the capability to defeat any threat that they would throw at us and I am more confident -- even more confident today," Syring added.

The test cost about $244 million, according to Syring.

"We are launching an interceptor that is flying thousands of miles past Hawaii and that requires us to shut down large parts of the ocean in terms of mariner ship traffic and air traffic," he said.

The next test will take place in August/September 2018 and will involve multiple interceptors attempting to take out a single test ICBM.

"We shoot more than one in a real world operational scenario," Syring said.

Experts express caution

While the Pentagon is calling this test a success, some experts cautioned that the $40 billion missile defense system still has a long way to go before it can be considered fully developed.

"It marks two successes in a row, which is significant, but only two hits out of the last five attempts; that is, only a 40% success rate since early 2010," said Philip E. Coyle, a senior fellow at the Center for Arms Control and Non-Proliferation.

"In school, 40% isn't a passing grade," added Coyle, who formerly headed the Pentagon's office of operational test and evaluation. "Based on its testing record, we cannot rely upon this missile defense program to protect the United States from a North Korean long-range missile."

Washington Rep. Adam Smith, the top Democrat on the House Armed Services Committee, congratulated the Missile Defense Agency for a successful test but sounded a note of caution that "much work remains to be done to ensure we have a reliable and effective system."

"After an investment of more than $40 billion since 2002, it's good that the Missile Defense Agency is finally doing a missile defense test against an ICBM target, some 13 years after the first Ground-Based Interceptor system's deployment," Smith told CNN.

"Flight intercept testing, particularly against realistic targets, remains a key element of the program to assess the effectiveness of our deployed missile defense system, as well as to demonstrate the capability and continue the development of such a system," he added.

Wake of North Korea threat

The test comes just two days after Pyongyang fired a short-range ballistic missile that traveled an estimated 248 miles, splashing down within Japan's exclusive economic zone.

In a Monday tweet, President Donald Trump joined the leaders of South Korea and Japan in condemning the test, saying that North Korea had "shown great disrespect" for China by "shooting off yet another ballistic missile."

North Korea has shown great disrespect for their neighbor, China, by shooting off yet another ballistic missile...but China is trying hard! — Donald J. Trump (@realDonaldTrump) May 29, 2017

The Pentagon insists the long-planned test of its ground-based interceptor system is not solely about North Korea, and the test is aimed at being able to challenge any threatening ICBM, including possibly from Iran in the future.

That test involved firing a new version of the military's single long-range ground-based interceptor missile, which is currently based in Alaska and California. That program has also been in existence for more than a decade but only about half of the tests have been successful, according to the Defense Department. US officials often call it a high-speed effort to hit a bullet with another bullet.

In the most recent Pentagon report examining weapons testing across the Department of Defense, this long-range system was criticized, saying it "demonstrates a limited capability to defend the US homeland from small numbers of simple intermediate-range or intercontinental ballistic missile threats launched from North Korea or Iran."

The report went on to say the Defense Department continues to discover new failure modes during testing.

Hitting a bullet with another bullet

In Tuesday's test, an interceptor missile was launched from Vandenberg and intercepted a simulated threat missile over the Pacific Ocean launched from Kwajalein Atoll in the Marshall Islands.

The interceptor tested had an upgraded "kill" vehicle -- to hit the incoming missile, as well as an upgraded booster and improved guidance.

With this pre-programmed test, the Pentagon was looking to see specifically how all these components performed and what additional improvements needed to be made. It is widely acknowledged that in a real world attack, several interceptors would be launched to maximize the chance of quickly destroying the incoming threat.

Last week, Director of National Intelligence Dan Coats told Congress, "North Korea is an increasingly grave national security threat to the United States because of its growing missile and nuclear capabilities combined with the aggressive approach of its leader Kim Jong Un. Kim is attempting to prove that he has the capability to strike the US mainland with a nuclear weapon."

Sen. John McCain, the chairman of the Senate Armed Services Committee, said in an interview Sunday that it would not be acceptable for North Korea to acquire an intercontinental ballistic missile, saying the US should not be reliant solely upon missile defense to ward off the threat.

"I don't think it's acceptable for the United States of America to have an intercontinental ballistic missile -- or a missile aimed at Australia -- with a nuclear weapon on it, and depend on our ability to counter it with an anti-missile capability," McCain told Australia's ABC.

He added that the situation on the Korean Peninsula had the potential to mirror the Cuban Missile Crisis unless Pyongyang is curbed, calling on China to do more.

Tuesday's test came as the US has ramped up other missile defense efforts, including the deployment of the THAAD missile defense system to South Korea which is designed to counter short, medium and intermediate range missile threats. Earlier this month, the US military announced that the THAAD missile defense system had become operational.