US President Donald Trump had earlier abruptly ordered the Pentagon to "substantially reduce" the Ulchi Freedom Shield exercise just before it began Monday.
Trump cited what he described as a good relationship with North Korean leader Kim Jong-un and South Korea's refusal to support him over the war in Iran.
South Korea's military said the Ulchi Freedom Shield, a command post exercise with the US, ended on Friday.
The August exercise was initially reportedly scheduled to be held in two phases for 11 days in simulation of North Korean attacks - the first part until Friday on defensive operations and the second part until August 27 on counteroffensive operations.
North Korea is extremely sensitive to the second phase.
South Korea and the US had also planned to hold 14 joint field training exercises during the Ulchi Freedom Shield period.
But they have agreed to halve them as well, according to South Korea's military.
Kim Yo-jong, the influential sister of North Korean leader Kim Jong-un, brushed aside Trump's overture on Wednesday, saying that reducing the duration and size of the drills won't change their "provocative, aggressive nature".
The next day, North Korea fired about 10 short-range ballistic missiles towards the sea, apparently following through with its previous threat to respond to the US-South Korean drills that it views as an invasion rehearsal.
Kim Yo-jong's statement dampened hopes for an early resumption of talks between Trump and Kim Jong-un, whose earlier nuclear diplomacy collapsed in 2019.
Kim Jong-un has used the diplomatic stalemate to increase his leverage by modernising his nuclear and missile arsenals and aligning with Russia over its war against Ukraine.
Kim Jong-un suggested in 2025 that he will not return to talks unless the US drops its demand for North Korean denuclearisation as a precondition for diplomacy.
With its supply of ammunition and troops to Russia, North Korea is likely receiving economic and military assistance in return, and its expanding ties with Russia provides it with leverage to ask for greater support from China, its biggest trading partner.
Kim Yo-jong denied Trump's claim that Kim Jong-un had responded to his request for a conversation.
When asked by reporters Wednesday if he would be meeting with Kim Jong-un this year, Trump said, "Yeah, I will be."
The Ulchi Freedom Shield is one of the main military exercises conducted by the US and South Korea annually to enhance their ability to cope with potential North Korean aggression.
Its downsizing has caused worries about joint US-South Korean readiness.
