Korean National Assembly Speaker Kim Jin-pyo, right, bumps fists with U.S. House Speaker Nancy Pelosi prior to their talks at the National Assembly in Seoul, Thursday. Yonhap

National Assembly Speaker Kim Jin-pyo and U.S. House Speaker Nancy Pelosi said Thursday they agreed to support efforts by Seoul and Washington for the denuclearization of North Korea, voicing concerns over the North's escalating threats.

"The two sides expressed concern over the grave situation in which North Korea's level of threat is heightening," said Kim, reading a joint press statement following a meeting between the two speakers.

"Based on a powerful and extended deterrence against North Korea that our public can recognize, we agree to support the two governments' efforts for denuclearization and peace through international cooperation and diplomatic dialogues," the statement said.

The speakers noted the expanding ties between the allies, mentioning how the South Korea-U.S. alliance has been widening to areas, such as defense security, the economy and technology.

To better support these ties, Kim said the speakers agreed on reviewing a resolution marking the 70th anniversary of the two countries.

Calling security, economics and governance the "three pillars" of the congressional delegation's visit here, Pelosi emphasized that the relationship between Seoul and Washington in these areas is "very strong" and that the two countries "learn from each other."

"This is special for us because the U.S.-Republic of Korea relationship is special to us," she said, noting how "a relationship that began from urgency and security many years ago has become the warmest of friendships."