"We will keep watching all the possibilities [of retaliation]. The international community is continuing to raise issues with the iniquity of China's [retaliative] measures," Cho told a press briefing.
The spokesman reiterated the reasoning behind the THAAD system deployment as "to respond to North Korea's sophisticated nuclear and missile threats."
On Wednesday, US Pacific Command Commander Adm. Harry Harris said that THAAD would be operational "in the coming days."
The THAAD agreement was reached by Seoul and Washington in July 2016. The move came amid growing tensions spurred by North Korea's recurring ballistic and nuclear tests.
The THAAD system has a range of some 200 kilometers (125 miles) and is designed to intercept short, medium and intermediate ballistic missiles at the terminal incoming stage. The move has been criticized by neighboring China and Russia as inappropriate, possibly disproportionate, and affecting other countries' interests.
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