WASHINGTON -- The United States is "most interested" in having talks with North Korea, but only when the regime is serious about giving up its nuclear weapons program, a State Department spokesperson told Yonhap News Agency Monday.

Heather Nauert said in an interview that Pyongyang is not showing an interest in dialogue when it continues to launch ballistic missiles and test nuclear weapons.

The US, through its "peaceful pressure campaign," will continue to put pressure and sanctions on Pyongyang in the hopes that the regime will come to the table, she added.

"We would prefer to have a conversation, to have a dialogue with North Korea," Nauert said. "However, we don't see that North Korea is even remotely interested in it at this point."

Last month Secretary of State Rex Tillerson acknowledged that the US is "probing" to see if North Korea is interested in talks. He said the two sides have been communicating through three direct channels.

"We are most interested in talking when the time is right," the spokeswoman said. "They're not showing an interest in that right now, but that is why we will continue to push forward with our peaceful pressure campaign."

US President Donald Trump is set to visit South Korea next month for bilateral talks with President Moon Jae-in. It will be part of his first trip to the region since taking office.

"President Trump and what he will do will only follow on what we have been doing here at the State Department," Nauert said. "We're following his lead, but we're all bolstering one another's work. We're all on the same page, pushing for the denuclearization of the Korean Peninsula and helping to make sure our allies understand we are firmly behind that."

Deputy Secretary of State John Sullivan is on a trip to Tokyo and Seoul this week.

He is scheduled to hold trilateral talks with his South Korean and Japanese counterparts in Seoul on Wednesday.

They will focus on "strategic coordination related to the urgent threat from (North Korea's) advancing nuclear weapons program," according to the State Department.

Sullivan will also hold bilateral meetings in both countries.

In Seoul, he plans to visit the demilitarized zone separating the two Koreas, Nauert said.

Tensions have run high in the wake of North Korea's ballistic missile launches and sixth and most powerful nuclear test in September. Pyongyang has been pushing to acquire the capability to strike the US mainland with a nuclear weapon.

Trump and the North Korean leadership fueled the tensions by calling each other derogatory names and threatening to take military action against each other. (Yonhap)