The United States said Thursday it will continue to be a "steadfast ally" of South Korea and expressed hope for "a productive relationship" with the country's next president after former President Park Geun-hye was ousted from office.

"We will continue to work with Prime Minister Hwang (Kyo-ahn) for the remainder of his tenure as acting President, and we look forward to a productive relationship with whomever the people of South Korea elect to be their next president," State Department acting spokesman Mark Toner said.

Toner said the US takes no position on the impeachment, but it respectshe decision.

"It is up to the Korean people and their democratic institutions to determine the future of their country, and we respect their decisions," he said.

"The United States continues to be a steadfast ally, friend, and partner to the ROK. The US-ROK alliance will continue to be a linchpin of regional stability and security, and we will continue to meet all our alliance commitments, especially with respect to defending against the threat from North Korea," he said.

Park was removed from office as the Constitutional Court unanimously upheld her impeachment.

She was impeached by the National Assembly on Dec. 9 on charges of letting a close friend meddle in state affairs, colluding with her to extort money from conglomerates, and neglecting her duties during a 2014 ferry sinking that killed more than 300.

Earlier in the day, Toner said during a regular briefing that the "fundamental ties and bonds" with South Korea will remain strong even if "governments change, administrations change, new leadership comes into office."

"We're very committed to our partnership with South Korea and look forward to strengthening it," he said.

Toner also said South Korea is "a strong ally, regional partner" and Secretary of State Rex Tillerson looks forward to meeting with his Korean counterparts when he travels to the region next week. (Yonhap)