South Korean President Lee Jae Myung said Tuesday that maintaining peace was "most important" for the country, but it needs to prepare for the "worst case scenario."

His comments come after U.S. President Donald Trump ordered Defense Secretary Pete Hegseth to "substantially reduce" joint drills with Seoul so as to not "send a signal that is totally inappropriate and hostile" to North Korea.

In a Truth Social post Sunday stateside, Trump cited his "very good" relationship with North Korean leader Kim Jong Un, and described the country has "unthreatening and respectful."

Lee on Tuesday said that the annual exercises, known as Ulchi Freedom Shield, are defensive and not intended to attack North Korea or raise tensions on the peninsula, according to a CNBC translation of the Korean release.

The joint military exercises that started Monday are scheduled to run until Aug. 27, with about 18,000 South Korean military personnel participating.

Pyongyang has long denounced the joint drills, calling them a rehearsal for invading the North.

The country's foreign affairs ministry said in a statement last week that "By doing so, [the U.S.] did not conceal its aim to complete preparations for the substantial military confrontation" with North Korea.

"This is tantamount to an admission that the exercises, which the U.S. and the ROK describe as 'annual' and 'defensive' ones, are a rehearsal for an aggressive war," it added.

Trump's comments also come as he accused Seoul of not helping the U.S. in the conflict with Iran, saying on Monday that "We have 39,000 soldiers over there guarding you from Kim Jong Un, your next door neighbor, and you're not going to help us on a very easy military operation in Iran."

U.S. Forces Korea, the command authority for Washington's forces in South Korea, consists of about 28,500 personnel.

Officials from South Korea's presidential office said that "We are closely discussing practical and military contribution measures with the U.S. side, taking into account various factors such as readiness on the Korean Peninsula and domestic legal procedures," South Korean media reported Monday.

Trump, using his rhetoric and timing around the exercises, is trying to entice North Korea's Kim into meeting with him, according to Victor Cha, Korea chair at the Center for Strategic and International Studies.

Speaking on a podcast by CSIS, Cha added that "this is not something that is unusual. We have seen the president use military exercises as a tool in the past."

Back in 2018, Trump had suspended exercises with South Korea as negotiations were going on between Pyongyang and Washington.

Cha also said that part of the reason we are seeing this now is because to Trump, the timing of the exercises are a useful instrument to send a concrete message, and to get headlines off Iran.

"Trump's tired of Iran ... so he's shifting to something else."

— CNBC's Jenny Lee contributed to this report.