The leaders of Japan and the United States have said the time for dialogue with North Korea is over, just as South Korea slapped a new raft of unilateral sanctions against Pyongyang.

Japan's Prime Minister Shinzo Abe on Monday met with US President Donald Trump, who is in Tokyo as part of a 12-day tour of five Asian countries.

His trip, focused both on trade and North Korea's nuclear missile programme, comes at a time of heightened tensions on the Korean Peninsula.

Speaking at a joint news conference dominated by North Korea, Abe said Japan and the US are in complete agreement about what measures should be taken against Pyongyang.

"There is no point in dialogue for the sake of dialogue with North Korea - now is the time not for dialogue, but for applying maximum level of pressure on North Korea," Abe told reporters.

"We completely agreed that in order to make North Korea change their policy, Japan and the US must take leadership in closely collaborating with the international community so that we can enhance the pressure to the maximum level over North Korea through all possible means."

For his part, Trump, who has repeatedly made highly-combative remarks against North Korea in recent months, including calling leader Kim Jong-un "little rocket man" and "madman", reiterated his stance that "the era of strategic patience [with North Korea] is over" and called it "a threat to the civilised world".

"Some people said that my rhetoric is very strong, but look what's happened with very weak rhetoric over the last 25 years - look where we are right now," Trump told the same press conference.

Al Jazeera's Scott Heidler, reporting from Tokyo, said "there was a full consensus" between Trump and Abe about how to deal with North Korea.

"Both leaders talked about the need for more pressure to be applied to North Korea ... and that they need the assistance of Russia and China," he said.

'Ground invasion'

On Sunday, two days before Trump's visit to South Korea, Pyongyang warned the US president against making "foolish remarks".

"If the US misjudges the DPRK's [North Korea] toughest will and dares to act recklessly, the latter will be compelled to deal a resolute and merciless punishment upon the former with the mobilisation of all forces," ruling party newspaper Rodong Sinmun said in a commentary published by the KCNA state news agency.

The latest war of words came after the emergence of a letter in which a top US defence official said that the only way to secure North Korea's nuclear weapons sites would be via ground invasion.

"The only way to 'locate and destroy - with complete certainty - all components of North Korea's nuclear weapons programs' is through a ground invasion," Rear Admiral Michael Dumont said in a letter responding to a request by two Congress members inquiring about casualty assessments in any conflict with Pyongyang.

Ted Lieu, a Congress member whom the letter was addressed to, posted a copy of it on his website.

Separately on Monday, South Korea said it had added 18 North Korean individuals to a blacklist banning its people and entities from transacting with them.

The people on the list include heads and ranking officials of five North Korean banks stationed in countries such as China, Russia and Libya, according to a statement on the South Korean government's official gazette.

The move, seen as symbolic due to the absence of economic relations between the two countries, comes after a new round of sanctions announced by the UN Security Council in the wake of the North's latest nuclear test in September.