"The THAAD defensive missile system is critical to protecting South Koreans from Kim Jong Un's growing arsenal. I hope any environmental concerns related to the full deployment of THAAD will be dispelled with a quick and thorough review," Royce said in a statement released Wednesday night.

"We need to use every tool at our disposal ?- including additional sanctions -? to address the Kim regime's threats. And we must continue to press China and Russia to play more productive roles, since North Korea's nuclear program endangers us all," he said.

The suspension could be seen as a setback to US efforts to fully deploy the system as soon as possible.

On Wednesday, the US Defense Department said it "trusts the ROK official stance that the THAAD deployment was an Alliance decision and it will not be reversed."

During a Senate Appropriations subcommittee hearing Wednesday, Sen. Dick Durbin expressed frustration about the suspension.

"This THAAD missile defense system for medium range missiles seems so obvious to me, for the people living in South Korea to protect them and to protect our forces who are there in their defense," the senator said.

"I'm troubled by the fact that it is now going to be resubmitted for political debate in the Republic of Korea as to whether or not they will except our $923 million investment in missile defense for their country. I can't follow their logic here," he said. (Yonhap)