In a press release they said they conveyed South Koreans' concerns about North Korea's evolving military capabilities and their growing support for the deployment of U.S. nuclear assets, which were withdrawn in 1991, and even the country's own nuclear armament.

"The State Department expressed its understanding of Koreans' concerns but was negative to the idea of redeploying tactical nukes out of concern about a possible escalation of regional tension and in line with the U.S. position toward denuclearization (of the Korean Peninsula)," they said in the statement. 

Eliot Kang, acting assistant secretary of state, told them he will relay the party's request to Secretary of State Rex Tillerson.

"Though there was no change in the State Department's position regarding the relocation of nuclear assets, we sensed remarkable changes around the U.S. Congress and think tanks," Rep. Yoon Young-seok told reporters. (Yonhap)