The U.S. State Department urged North Korea on Tuesday to "return to engagement" as the North threatened retaliatory action against South Korea over anti-Pyongyang leaflet campaigns.

A spokesperson of the department told Yonhap News that the U.S. remains in "close coordination" with its ally, South Korea, and urged North Korea to return to engagement.

The spokesperson made the remarks when asked about the North's threat to send anti-Seoul propaganda leaflets and move to install loudspeakers near the inter-Korean border. 

This week, North Korea threatened to send some 12 million propaganda leaflets into the South and appears to have set up around 20 loudspeakers near the border area.