Choo Mi-ae, who is Chairwoman of South Korea’s ruling party, warned that the US President must consult with her government in Seoul before any military action was taken against their unruly neighbours.
Speaking in Washington DC Ms Choo said that “a peaceful resolution” must continue to be sought.
She said: “President Trump often emphasises that he put all options on the table.
“We want to make sure that this option of another war is not placed on the table.
There are fears that if the US was to use its military force on North Korea, the corrupt regime may retaliate with an attack on the South.
Reinforcing her point Ms Choo added: “Under no circumstances should the US go ahead and use a military option without the consent of South Korea.”
Mr Trump visited South Korea earlier this month as part of a two week long tour of Asia.
Addressing South Korea’s National Assembly last Wednesday Mr Trump insisted that the US would “not be intimidated” by Kim Jong-un’s rhetoric and called for other countries to respond to the “twisted regimes” threats with a sign of military force.
He also warned the “three largest aircraft carriers in the world are appropriately positioned” to face Pyongyang.
Prior to his intervention in South Korea, Mr Trump had previously suggested he was ready to use the US military to attack the rogue country.
At the start of last month, he said his Secretary of State’s efforts to negotiate with North Korea were a waste of time.
On Twitter, he said: “I told Rex Tillerson, our wonderful Secretary of State, that he is wasting his time trying to negotiate with Little Rocket Man…
“…Save your energy Rex, we’ll do what has to be done!
“Being nice to Rocket Man hasn’t worked in 25 years, why would it work now? Clinton failed, Bush failed, and Obama failed. I won’t fail.”
During last week’s trip to Asia, the US president also met with the Chinese President Xi Jinping.
He called on the Beijing leader to do more to stop North Korea.
However, upon his return to Washington Mr Trump said he would not advocate a plan which would see the US and North Korea both agree to stop conducting major military exercises in the area.
He said: “We agreed that we would not accept a so-called ‘freeze for freeze’ agreement like those that have consistently failed in the past.”