My nuclear button is 'more powerful': Trump tells North Korea

US President Donald Trump today warned that his "nuclear button" is "much bigger and more powerful" than the one controlled by North Korea's Kim Jong Un, as the White House said it was keeping all of its options on the table to curb Pyongyang's atomic programme.

Trump's response followed a New Year's Day address by Kim, who said that North Korea's nuclear weapons can reach anywhere in the US and threatened that he has a nuclear button on his desk.

The two leaders have threatened one another's countries with nuclear weapons repeatedly over the last year.

"North Korean Leader Kim Jong Un just stated that the Nuclear Button is on his desk at all times. Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!" Trump said in a tweet.

In a televised address to the nation, Kim had said the entire area of the US mainland is within North Korea's nuclear strike range.

In the same address, the North Korean leader also said his country needs to mass-produce nuclear warheads and ballistic missiles and accelerate their deployment.

The White House called North Korea "a global threat" and asked countries to step up pressure against it.

"The focus here is to apply maximum pressure on North Korea and the US wants other countries to join it in this,"

White House Press Secretary Sarah Sanders told reporters.

"This is a global threat, which is why we're calling on everybody to step up and do more and we're going to continue working with a lot of different leaders and other countries to help do that," she said.

Sanders said the US is keeping all its options "on the table".

Earlier, Trump said the US-led international sanctions and "other pressures" are beginning to have a big impact on the authoritarian North Korean regime after its leader Kim called for a breakthrough in relations with South Korea and said Pyongyang might attend the 2018 Winter Olympics to be held in the South Korean city of Pyeongchang.

South Korea welcomed the North Korean offer and proposed holding high-level talks with Pyongyang.

Sanders said the developments would not change US'

relations with South Korea "which remains stronger than ever".

"We're going to continue to work with South Korea to put maximum pressure on North Korea and work towards the ultimate shared goal that we both have," she said in response to a question.

North Korea last year increased the pace of its missile programme. Since February, Pyongyang has fired off 23 missiles. On November 29, the North Korean leader said that his country had achieved full nuclear statehood after what he said was the successful test of a new missile capable of striking anywhere in the United States.

Fears of a catastrophic conflict between the US and North Korea spiked as the leaders of the two nations taunted each other, with Trump calling the North Korean leader 'Rocket Man'.

The US and its allies, including Japan and South Korea, have put increasing economic pressure on North Korea in an attempt to halt the reclusive regime's nuclear and missile development.