The whirlwind diplomacy since US President Donald Trump's snap decision in March to meet North Korean leader Kim Jong Un has left Tokyo out in the cold.

Japanese Prime Minister Shinzo Abe, 63, flew to the US the following month to remind Mr Trump that any deal on North Korea's nuclear programme must take into account Tokyo's concerns about the missile threat from Pyongyang.

Last year, North Korea flew two missiles over Japan's northern island of Hokkaido. One was timed to mark the 107th anniversary of the Japan-Korea Treaty of 1910, under which Tokyo colonised the Korean peninsula.

Mr Trump, in a White House statement, slammed the missile launches and warned that "all options are on the table".

While Japan and South Korea are both US allies under the US nuclear umbrella, their proximity to North Korea means their residents, as well as US troops based in the two countries, are sitting ducks for North Korea's short-and intermediate-range missiles.

Mr Kim's pledge on April 21 to halt nuclear tests and intercontinental ballistic missile launches did not mention short-and intermediate-range ballistic missiles.

Now that the US has apparently hit the pause button and taken a harder stance on the North, the hawkish Mr Abe would have more time and leeway to recalibrate Japan's policy towards the North.

It can offer carrots in the form of humanitarian aid, food aid and war reparations to get Pyongyang to release Japanese nationals abducted to work as spies for the Kim regime. Mr Abe, facing a party leadership vote in the coming months, has made this a key issue during his political career.

With input from Japan Correspondent Walter Sim