A top U.S. military commander has said he believes North Korea is capable of firing a nuclear missile that can reach the continental United States, but the country's ready to defend against such attacks.

Adm. William Gortney, commander of U.S. Northern Command, made the remark at a think tank event Wednesday, saying he agrees with the intelligence community's assessment the North has the ability and technology to put nuclear weapons "on rockets that can range the homeland."

It's not the first time Gortney made such remarks. In April he also said the North is believed to be capable of miniaturizing nuclear warheads to put on its new KN-08 intercontinental ballistic missile and fire it at the U.S. mainland.

The commander said North Korean leader Kim Jong-un is very unpredictable.

"No one really understands the great leader," Gortney said, according to the Defense Department. "But we're ready for him ... We're ready 24-hours-a-day if he's dumb enough to shoot something at us."

Gortney's assessment of the North's miniaturization capabilities is not in line with the official U.S. government position.

In May, the National Security Council at the White House said the U.S. does not believe the North the capacity to build nuclear warheads small enough to fit atop missiles. That assessment came in response to Pyongyang's claims that it can produce "smaller nukes."

North Korea has conducted three underground nuclear tests so far, in 2006, 2009 and 2013. The country has also conducted a series of long-range missile or rocket launches since 1998. In its most recent launch in late 2012, the North succeeded in putting a satellite into orbit.

Analysts have warned that it is only a matter of time until the North develops nuclear-tipped missiles. Some experts have recently warned that the communist nation's nuclear arsenal could expand to as many as 100 bombs by 2020. (Yonhap)