Donald Trump has said the US is considering stopping all trade with any country that does business with North Korea.

His announcement in a tweet could be aimed primarily at China, which is Pyongyang's only major ally and a key trading partner.

Tensions between the US and North Korea have increased after Pyongyang said it had tested a hydrogen bomb - its sixth and most powerful nuclear detonation to date.

The US President has been meeting his military chiefs and when asked by reporters earlier if America would attack North Korea, he replied: "We'll see."

Image: North Korea's Korean Central News Agency released this photo of Kim Jong Un inspecting a device

His defence secretary, General James Mattis, said any threat to the US, its territories or its allies by Pyongyang would be met with a "massive military response".


He said America was "not looking to the total annihilation" of the North but "we have many options to do so".

Writing on Twitter, Mr Trump has warned that appeasing the North will not work, adding: "They only understand one thing!"

The United States is considering, in addition to other options, stopping all trade with any country doing business with North Korea. — Donald J. Trump (@realDonaldTrump) September 3, 2017

He said the regime's "words and actions continue to be very hostile and dangerous to the United States".

He also denounced the secretive country as a "rogue nation which has become a great threat and embarrassment to China, which is trying to help but with little success".

:: Nuclear test was diplomatic weapon to divide US and China

US Treasury Secretary Steven Mnuchin said he would compile a new sanctions package, potentially to cut off all trade with North Korea.

The UN Security Council is set to discuss the crisis on Monday.

The story of N Korea's nuclear tests

South Korea has called for the "strongest possible" response, including new UN sanctions to "completely isolate" its northern neighbour.

Seoul's national security adviser, Chung Eui Yong, said there had been talks with Washington about deploying US strategic military assets to the Korean peninsula.

Seoul's defence ministry said the US and South Korean military chiefs have spoken on the telephone and agreed the test was "a provocation that cannot be overlooked".

The chairmen of the joint chiefs of staff, General Jeong Kyeong Doo and General Joseph Dunford, "agreed to prepare a South Korea-US military counteraction and to put it into action at the earliest date".

China said it strongly condemned the detonation.

President Xi Jinping and Russian leader Vladimir Putin have agreed to "appropriately deal with" the latest test and "stick to the goal of denuclearisation on the Korean Peninsula".

And Japan's foreign minister, Taro Kono, described the new explosion as "extremely unforgivable".

Foreign Sec': ‘None of the military options are good’

The device, which is thought to have been about five times larger than the bomb dropped on the Japanese city of Nagasaki in World War II, caused a manmade earthquake.

:: Key steps in North Korea's nuclear and ballistic missile ambitions

Pyongyang said via state media that it had detonated a hydrogen bomb with "perfect success".

It claimed the device could be mounted on its newly developed intercontinental ballistic missiles, which experts have said are capable of reaching the US mainland.

There has been no independent confirmation the detonation was a hydrogen bomb rather than a less powerful atomic weapon of the kind Pyongyang has tested in the past.

Prime Minister Theresa May said the "reckless" nuclear test posed an "unacceptable further threat to the international community".

What action could be taken against N Korea?

Foreign Secretary Boris Johnson said if North Korea managed to fit a hydrogen bomb to a "successful missile" it would "unquestionably present a new order of threat".

Concerning the way ahead, Mr Johnson said that "none of the military options are good".

But on sanctions, he pointed out that China is responsible for 90% of North Korea's trade, adding that Kim Jong Un's nation has only six months of oil supplies left.

He said Britain's message to Beijing was: "We think there's more scope, for you the Chinese, to put economic pressure on the North Koreans."