"Unfortunately yet predictably, China responded to the arrival of THAAD with vague threats against the United States and South Korea. In recent months, China has waged a campaign of diplomatic bullying and economic coercion against South Korea in an attempt to stop the deployment of THAAD," Sen. John McCain (R-AZ) said in a statement.

"But the reality is that this missile defense system is only necessary because China has aided and abetted North Korea for decades. If China has genuine concerns about the deployment of THAAD in South Korea, it should cease its attempts to undermine South Korea's sovereign ability to defend itself and use its considerable influence to pressure North Korea to stop its destabilizing behavior," he said.

McCain also welcomed this week's arrival of THAAD elements, saying the North's missile launches earlier this week were a reminder of the grave threat North Korea poses and demonstrate the "wisdom and necessity" of the decision to deploy THAAD.

Sen. Tom Cotton (R-AR) said China shouldn't have a say over what the US does to protect itself.

"Beijing does not dictate to the United States what we can and cannot do to protect ourselves and our allies," he said in a statement.

Had China been so concerned about THAAD, it should have "put its foot down years ago and brought to reason the country that's done the most to provoke one: North Korea."

"Instead, China has given a pass to the regime's reckless behavior for far too long. The US will do whatever it takes to keep our country and our allies safe, and there's no moral equivalence between our self-defense and North Korea's aggression," he said. (Yonhap)