Six first-term lawmakers of South Korea's main opposition party will visit China this week despite an open appeal from the presidential office to reconsider the trip, a party spokesman said Sunday.

The presidential office Cheong Wa Dae issued a statement earlier in the day urging the lawmakers of the Minjoo Party of Korea to cancel the trip scheduled for Monday through Wednesday.

The group, led by Rep. Kim Young-ho, plans to meet with Chinese Communist Party officials and academics to hear their views on the growing diplomatic row over the Terminal High Altitude Area Defense system set to be placed in South Korea by end-2017.

China has strongly protested Seoul and Washington's recent decision to deploy THAAD in the face of North Korea's missile and nuclear threats, saying the system hurts its strategic security interests.

"The visit has already been confirmed as part of our parliamentary diplomacy, and it is a promise in international diplomacy that cannot be canceled for domestic political reasons," Ki Dong-min, floor spokesman of the MPK, said in a written briefing released after an impromptu meeting among the six lawmakers. "The six lawmakers of the MPK will take part in the parliamentary diplomacy boldly and prudently, with keen consideration for our national interests."

Cheong Wa Dae also rejected China's criticism of the THAAD decision, saying the system wouldn't be needed if North Korea's nuclear and missile threats disappeared.

It urged China to take issue with North Korea instead of raising questions over South Korea's "purely defensive measure."

Ki expressed hope the lawmakers' visit will help develop diplomatic ties between the countries.

"The Park Geun-hye administration should also work harder to improve ties with China," he added. (Yonhap)