Thornton's statement came after reports of a possible delay caused by remarks by a White House advisor who was accompanying U.S. Vice President Mike Pence on his trip to Seoul.
U.S. Vice President Mike Pence has once again pledged the Trump administration's commitment to defending its allies in Asia from North Korea and any other threats.
Wrapping up the lecture attended by some 70 South Korean and U.S. business leaders, Pence left through Osan Air Base for Tokyo, where he met with Japanese Prime Minister Shinzo Abe and discussed North Korea's evolving nuclear and missile threats.
Pence's advisers said the vice president would seek to make the case to Abe and Aso that the USA rejection of the Trans-Pacific Partnership, or TPP, under Trump did not signal a US withdrawal from trade and economic development in the region.
"We have to be honest about where our trade relationship is falling short", he said.
The U.S. military says an aircraft carrier participated in curtailed training with Australia before starting its journey north toward the Korean Peninsula.
On the campaign trail, Trump criticized the South Korea-US free trade agreement as a "job killer" especially for the US auto industry, and immediately already pulled out of the 12-nation Trans-Pacific Partnership after taking office.
On Monday, Pence sent a robust warning to Pyongyang during a joint news conference with acting President and Prime Minister Hwang Kyo-ahn. Pence said he and the president are heartened by the support of allies across the Asia-Pacific region, including China, adding that all will continue to advance that objective.
"I think at the 100-day marker, the American people are going to conclude what I have concluded: President (Donald) Trump is off to a great start".
While inspecting the Demilitarized Zone between North and South Korea, Pence warned Pyongyang that after years of testing the US and South Korea with its nuclear ambitions, "the era of strategic patience is over". Dent said the relocation efforts for Japan and South Korea have been in the works for some time.