The U.S. is stepping up its response to ongoing threats from North Korea, just as President Trump says he'd be willing to meet with leader Kim Jong Un. 

Officials have confirmed a U.S. anti-missile system based in South Korea is now operational and can defend against North Korean missiles.

The controversial installment of the Terminal High Altitude Defense System (THAAD) has been met with opposition from China, which worries the system's radar could be used to spy into its territory.

Another issue is who will be footing the bill for the billion dollar system? The President has said South Korea should, but the South Korean Defense Ministry has repeatedly said it would only provide the space.

Meanwhile, CIA Director Mike Pompeo made a surprise visit to South Korea Monday after another round of missile tests were made by North Korea this weekend. A missile fired Saturday exploded minutes after liftoff.

Pompeo is the third senior administration official from Trump's national security team to visit the area amid growing tensions. Despite elections in South Korea next week, Pompeo has no plans to meet with any of the presidential candidates.

In an interview with Bloomberg News, President Trump said that he'd be "honored to meet with North Korean leader Kim Jong Un if the circumstances were right."

Secretary of State Madeleine Albright was the last administration official to meet with a leader from the nation back in 2002.

But in recent weeks, Secretary of State Rex Tillerson said the only way the U.S. would negotiate with North Korea is if the regime made credible steps towards giving up its nuclear weapons.