US President Donald Trump (Photo by Anadolu via Getty Images)

US President Donald Trump has threatened to downgrade its ties with South Korea over Seoul`s refusal to participate in the US-Israeli war on Iran.

In an interview with Fox News released on Sunday, Trump threatened that Washington may decide to reconsider the scope of US military presence in South Korea.

"We have very little help from other countries, and we help other countries; we spend billions and billions of dollars helping NATO and other countries, South Korea as an example."

He added he would be a "fool" if he did not punish Seoul for refusing to do as it was told by the US.

"When they are not willing to do anything for you, you can`t be a fool and help them."

Trump revisited the issue multiple times, even ordering a significant reduction in joint military drills with South Korea.

He told the Pentagon earlier this month to scale back joint military exercises with the South Korean military.

Trump had described the joint military exercises with South Korea as costly.

He also said that the annual joint military exercises were "hostile" towards North Korea and had called for them to be reduced, citing his relationship with Kim Jong-un.

Trump`s latest remarks renewed concerns among US allies, citing US foreign policy shifts as proof of Washington`s untrustworthiness.

Analysts say Trump is sending Washington`s allies mixed signals, citing the scale-back of joint military exercises with South Korea as another example of the Trump administration`s true lack of leadership.