The majority Democratic Party on Friday escalated its campaign against a US missile defense system and renewed calls on the Seoul government to obtain parliamentary approval over its deployment.

The center-left party, enjoying rising popularity after the ouster of Park Geun-hye from office, convened the first meeting of its expanded in-house committee on the issue of the Terminal High Altitude Area Defense system and demanded the ongoing deployment be immediately suspended.

The former main opposition party has expanded the THAAD committee's status and organization in an apparent bid to put further pressure on the government ahead of the May 9 presidential election.

Earlier this month, Washington began moving THAAD components to South Korea. The issue is expected to draw further media attention as US Secretary of State Rex Tillerson began his two-day visit to South Korea on Friday.

"The practical defense capabilities of the THAAD battery against North Korean missiles are limited," said Rep. Sim Jae-kwon, the head of the committee.

"The deployment has sparked a strong protest from China and caused further difficulties for the struggling South Korean economy," said Sim, who currently serves as the chairman of the National Assembly Foreign Affairs and Unification Committee.

He then reiterated his party's position that the government must earn the parliament's consent before installing the battery, as the project involves providing South Korean land to the US military.

While the government insists that the THAAD system is not subject to parliamentary approval and is only intended to defend the country against North Korean provocations, China and Moscow have been expressing strong discontent on concerns over the increased presence of a US military system in Northeast Asia.

China has been protesting Seoul and Washington's decision to deploy the THAAD system, rolling out economic retaliations, such as banning tour agencies from selling trips to South Korea.

Sim urged Acting President and Prime Minister Hwang Kyo-ahn to stop the deployment of the battery and focus on organizing a fair presidential election. (Yonhap)