Washington (CNN) -- The U.S. military's Missile Defense Agency will practice protecting the United States from a simulated Iranian missile attack next month in an exercise using the agency's newest missile-killing technology, Pentagon officials said Friday.

Previous tests have been focused on a missile trajectory that mimics an attack from North Korea, but the January test will have a trajectory and distance resembling an intercontinental ballistic missile launch from Iran.

At the same time, the agency will be testing its new "Capability-2" technology, with upgraded software and sensors loaded inside an interceptor missile that will be fired at the fake Iranian missile.

The Capability-2 technology is designed to eventually replace the existing hardware the United States has in its two missile defense bases in California and Alaska, according to Rick Lehner, a spokesman for the Missile Defense Agency.

While intelligence assessments of that country's capabilities now suggest an Iranian ICBM threat is as far away as 2020, this test was planned more than three years ago, when the threat seemed much closer, Lehner said.

In the January test, the fake ICBM is slated to originate from the Missile Defense Agency's launch facility in the Marshall Islands in the South Pacific while the interceptor missile will be launched from Vandenberg Air Force Base in California, according to Lehner.

Missile defense tests have been likened to hitting a bullet with a bullet. This test will be even more difficult: It will be like hitting a bullet head-on with another bullet, because any launch from Iran would have a trajectory that would require a U.S. interceptor missile hitting the target directly, Lehner said.

The missiles will be flying at speeds of between 17,000 and 18,000 miles per hour, according to Lehner, about 3,000 mph faster than tests involving mock North Korean missiles. The speed will reduce the strike window, meaning the interceptor, also known as the "kill vehicle," will have to work even faster at identifying and striking the target missile.

The United States has only two missile defense bases, one at Vandenberg, with three missiles, and the other at Fort Greely, Alaska, with 20 interceptor missiles at the ready.

Lehner said that if Iran were to launch an ICBM attack against the United States, the most likely defense option would be firing a missile from Alaska, because of the shorter distance around the globe.

The United States was prepared to put a third missile defense site in eastern Europe, but the Obama administration scrapped that option because of the reduced ICBM threat from Iran. In its place, the administration said it will move ships with the capability of shooting down short- and medium-range missile from Iran which, they say, pose a greater threat to Iran's neighbors and U.S. bases in the Middle East.