SEOUL (Reuters) - The United States is unlikely to cut back its forces in South Korea even if former U.S. president Donald Trump wins re-election, the South's minister tasked with matters related to neighbouring North Korea said in a television interview.

In the interview transmitted on Saturday, Unification Minister Kim Yung Ho told broadcaster KBS this was because the U.S. Congress had already decided the matter in a defense bill it recently passed.

"One of the concerns many people have is... the issue of any withdrawal of U.S. troops from Korea" if Trump is re-elected, Kim said.

But December's National Defense Authorization Act says the U.S. administration requires congressional approval to scale back the 28,500 troops in South Korea, Kim said.

Strengthening ties between the United States, South Korea and Japan would help overcome any political changes in the U.S., he added.

At Camp David last August, U.S. President Joe Biden and the leaders of South Korea and Japan agreed to strengthen military and economic co-operation.

The comments came in Kim's reply to a question on a Politico report that Trump was considering letting North Korea keep its nuclear weapons, and offering financial incentives to stop making new bombs - which Trump has denied as "fake news".

"Recognising North Korea as a nuclear power means that South Korea will have no choice but to develop nuclear weapons, and Japan (also)," Kim said, when asked about the views of some U.S. experts.

These analysts argue that North Korea should be recognised as a nuclear state and call for disarmament talks.

Neither the United States or South Korea can accept the prospect of recognising North Korea as a nuclear state, since that would trigger a domino effect leading to the collapse of the Non-Proliferation Treaty framework, Kim said.

The neighbours remain technically in a state of war since the Korean War from 1950 to 1953 ended in an armistice rather than a peace treaty.

(Reporting by Joyce Lee; Editing by Clarence Fernandez)