Will mediate between S Korea and Japan only when they ask for it: Trump

US President Donald Trump Friday showed his reluctance to resolve the ongoing trade tension between South Korea and Japan, saying he will mediate only when the two countries ask for it.

President Trump was told by the reporters about the ongoing tension between the two countries, which are close friends and allies of the United States.

Japan and South Korea have a series of disputes, including a widening trade row and spat stemming from colonial-era reparations.

"There's ongoing tension between Japan and Korea. In fact, the President of Korea asked me if I can get involved and I said: 'How many things do I have to get involved in? I'm involved with North Korea on helping you. I'm involved in so many different things'," Trump told reporters.

He has strong friendship with leaders of the two countries President Moon Jae-In of South Korea and Prime Minister Shinzo Abe of Japan. Only last month Trump visited both the countries.

"We just did a trade deal, a great trade deal with South Korea, but he tells me that they have a lot of friction going on now with respect to trade, primarily with respect to trade," Trump said.

Relations between Japan and South Korea have been strained for decades because of Japan's colonial occupation of the Korean peninsula in the early 20th century.

South Koreans have previously staged anti-Japanese demonstrations at the embassy in Seoul.

"Japan has something that South Korea wants, and he asked me to get involved. So maybe if they would both want me to, I'll be, it's like a full-time job getting involved in South Korea. But I like both leaders," he said.

"I like President Moon, and you know how I feel about Prime Minister Abe. He's a very special guy, also. So, if they need me, I'm there. Hopefully they can work it out but they do have tension, there's no question about it, trade tension," Trump said responding to the question on trade tension between Japan and South Korea.