North Korean dictator Kim Jong Un wants to develop nuclear weapons capable of striking the United States in order to clear the path for an invasion of South Korea, a defector diplomat told House lawmakers Wednesday.

“While Kim Jong Un has already long had the tools to destroy South Korea effectively, he also believes it is necessary to drive American forces out of the peninsula,” Thae Yong Ho told the House Foreign Affairs Committee during a Wednesday hearing. “And this can be done, he believes, by being able to credibly threaten the continental United States with nuclear weapons.”

Thae is a former senior diplomat who defected from North Korea in 2016 after a stint as the deputy ambassador to the United Kingdom.

There are about 25,000 American service members in South Korea, which hosts one of the largest U.S. military deployments in the world. North Korea emerged this year as a top foreign policy priority for President Trump’s team, as the regime has tested intercontinental ballistic missiles for the first time and detonated a hydrogen bomb over the summer.

“Today, Kim Jong Un thinks that only nuclear weapons and ICBMs can help him avert the continuing disintegration of the North Korean system,” Thae said in his opening statement.

Thae blamed the disintegration of North Korea on increased access to information, despite the government’s attempt to block access to South Korean media. “[T]he existence of a prosperous and democratic South Korea so close to the border is, by itself, a major threat towards his dynasty,” Thae said.

The Trump administration spearheaded an effort to impose multiple rounds of new sanctions on the North Korea through the United Nations Security Council. But China and Russia have insulated the regime from the full affect of such sanctions, according to western observers, and prevented the U.N. from imposing some of the stiffest sanctions.

Thae said the United States needs to impose “targeted sanctions” on the regime. But the effort to change the dictatorship’s strategy is complicated by a “misunderstanding” of American might.

“Frankly, Kim Jong Un is not fully aware of the strength and might of American military power,” Thae testified. “Because of this misunderstanding, Kim Jong Un genuinely believes that he can break the sanctions regime apart once he compels Washington to accept North Korea’s new status after successfully completing the development of his ICBM program and putting the new missiles into deployment.”