South Korea and the United States began their annual large-scale joint military exercise on Monday to better cope with threats by nuclear-armed North Korea, which has warned the drills would deepen regional tensions and vowed to respond to “any provocation” against its territory.

In a speech to mark the 80th anniversary of Korea's liberation from Japanese colonial rule, Lee said he would restore the so-called September 19 Comprehensive Military Agreement, a de-escalation measure that halted some military activities at the border between North Korea and South Korea.

The North Korean leader's powerful sister said on Thursday that the country has never taken down propaganda loudspeakers and will not do so, calling South Korea's belief that Pyongyang was responding to its peace overtures a "pipedream.