“Any discussion about the number of US troops is subject to the ROC’s invitation to have them there, and the discussions between the US and the ROC are separate and distinct from the negotiations that are going on with the DPRK. That issue will not come up in the discussions with DPRK… That issue is not on the table here in Singapore on the 12th nor should it be,” he said.

Speaking at the security summit Mattis added that the United States was committed to working with its allies in Seoul to secure a verifiable denuclearization of the Korean peninsula.

"On the Korean peninsula, we hold the line with our ally," he said. "Our objective remains a complete, verifiable, and irreversible denuclearization of the Korean peninsula."

Earlier, Trump and Kim expressed their willingness to meet on June 12 in Singapore as originally planned, the separate statements came after Trump abruptly cancelled the US-North Korea summit citing hostile comments by Pyongyang and stressing that he was looking forward to meeting with the North Korean leader "someday."

Trump reinstated the planned summit with North Korean leader Friday, telling reporters outside the White House that he thinks that the countries "going to have a relationship, and it will start on June 12."

More about: NorthKorea