President Trump's tweet comes after North Korean leader Kim Jong-Un's New Year address that he was always within reach of the nuclear button

My nuclear button 'bigger, more powerful' than North Korea's, says Trump

Amid the sanctions and rhetoric, US secretary of state Rex Tillerson has been using diplomatic back channels with the Korean government and its ally China

Declaring North Korea a terrorist state should have happened years ago: Trump

This is the first time all three US aircraft carriers are taking part at the same time in a military exercise in over a decade.

US aircraft carriers, South Korean destroyers conduct joint naval excercise

'We must act fast. And hopefully China will act faster and more effectively on this problem than anyone,' Trump said as he met with Chinese leader Xi Jinping in Beijing

Trump urges China & Russia to act fast on North Korea, warns 'time is quickly running out'

North Korean ambassador said sanctions on its country was affecting vulnerable families

Sanctions threatening women and children: North Korea

A Russian news agency quoted North Korea's foreign minister as saying Trump would be made to pay with 'a hail of fire'

North Korea says Trump has 'lit the wick of war': Russian media

The amphibious assault ship arrived at the Sasebo naval base in south-western Japan ahead of the first joint exercise among Japan, France, the US and the UK

French warship arrives in Japan for military drill amid tension over North Korea's missile launch