The controversial battery was hastily set up on a former golf course in southwestern Korea in the dying days of the last administration, apparently for fear that the new government would block it.

The floor leader of the ruling Minjoo Party, Woo Won-shik, said in a radio interview Wednesday, "We have to look into issues including the possibility of sending back THAAD if it didn't go through the proper legal procedures here." Woo later told reporters that his party agrees with Cheong Wa Dae on the matter.

Cheong Wa Dae and the ruling party want the National Assembly to vote on the deployment of a Terminal High-Altitude Area Defense battery from the U.S. here, which they say the Park Geun-hye administration pushed through without due process.

Hong Seok-hyun, Moon's special envoy to the U.S., told reporters that the THAAD issue was one of the points the president asked him to discuss with Trump administration officials.

And Chung Eui-yong, a former envoy to the UN in Geneva who now leads Cheong Wa Dae's security team, told the Chosun Ilbo in a telephone interview, "The president pointed out the need for democratic process in the deployment, whether or not there is a legitimate need to deploy the THAAD battery."

Ruling party officials stressed that this does not mean Cheong Wa Dae wants to send the THAAD battery back. Hong said the president's comments stressed on need for due process. Cheong Wa Dae and the ruling party do not plan to raise the matter before the summit with U.S. President Donald Trump next month.

Several high-ranking sources in the ruling party told the Chosun Ilbo that the Moon administration will first seek understanding from the U.S. before seeking National Assembly ratification of the THAAD deployment, and that there is "no reason to rush ratification through before the summit."

Meanwhile, Hong met U.S. President Donald Trump for 15 minutes, and Trump told him he is "willing to resolve the North Korean nuclear crisis through engagement under the right conditions."