SEOUL, Jan. 5 (Xinhua) -- South Korea on Thursday re-affirmed its position to deploy a U.S. missile defense system in its soil as planned despite strong opposition from neighboring countries.

Seoul's foreign ministry spokesman Cho June-hyuck told a press briefing that Terminal High Altitude Area Defense (THAAD) deployment in South Korea is a sovereign, self-defensive act to protect people's safety and the country's security from the Democratic People's Republic of Korea (DPRK)'s nuclear and missile threats.

His comments came a day after seven lawmakers of the biggest opposition Minjoo Party arrived in Beijing to talk with senior Chinese officials about the THAAD installation.

The main opposition party has opposed the U.S. anti-missile system's deployment. Major presidential contenders of the party pledged to review the THAAD deployment decision, calling for the current government to stop all of the deployment process to leave it to next government.

As President Park Geun-hye was impeached on Dec. 9, an early presidential election is widely expected to be held as early as April. If the constitutional court upholds the impeachment motion, an election must be held within 60 days.

Woo Sang-ho, floor leader of the Minjoo Party, said that diplomacy by lawmakers would be good under current situations that government officials fail to contact Chinese officials to resolve the THAAD issue.

The party's floor spokesman told a press briefing that Minjoo Party lawmakers are making diplomatic efforts that the government and the ruling Saenuri Party had failed to do.

The Saenuri Party and the new conservative party, composed of defectors from the ruling party, denounced visits by Minjoo Party lawmakers to China, describing it as disgraceful and humiliating.