The massive corruption scandal threatening to unseat South Korean President Park Geun-hye could paralyze her government for months to come and pose greater opposition to the planned deployment of the US THAAD missile defense system, a US expert said.

Park has been under growing pressure to step down following revelations that a long-time confidante, Choi Soon-il, exercised enormous influence over her and her handling of state affairs, while amassing huge ill-gotten wealth.

"Regardless of whether Park immediately resigns, the crisis threatens to paralyze the South Korean government for months," Scott Snyder, a senior Korea expert at the Council on Foreign Relations, said in an article in Newsweek magazine.

"It comes amid heightened anxieties in South Korea caused by the United States' transition to a Donald J. Trump presidency and North Korea's push to develop a long-range nuclear strike capability," he said.

As the opposition-controlled National Assembly is intent on paralyzing government functions as a message to Park that her decisions no longer carry legitimacy, the deployment of the Terminal High Altitude Air Defense (THAAD) system will now encounter heightened opposition, Snyder said.

"Park's impeachment or resignation would generate intense debate in the National Assembly. South Korea's constitution stipulates that resignation triggers an election within 60 days, but none of South Korea's political parties are prepared to field candidates in such a short time," he said.

South Korea and the US decided in July to deploy a THAAD battery to cope with growing missile threats from North Korea. But opposition parties have strongly opposed the decision, arguing that the system isn't effective in defending against the North and its deployment would only seriously sour relations with China.

China has called for scrapping the decision, seeing THAAD, especially its powerful "X-band" radar as a threat to its nuclear deterrent and other security interests, despite repeated assurances from Washington that the system is designed only to defend against the North.  (Yonhap)