President Donald Trump on Tuesday told reporters that North Korean leader Kim Jong Un "likes sending rockets up, doesn't he?" and added that he still calls Kim "Rocket Man."

It seems unclear as to how Trump in this instance was using the moniker and why he decided to revive it after first making the reference in September 2017. Trump did not elaborate when asked a follow-up question by a reporter and also did not post any comments about North Korea or Kim on Twitter.

Trump's vague and cryptic comment comes after Kim shot off two projectiles into the sea last week and after recently threatening Japan with a ballistic missile. North Korea has carried out over 100 missile tests since 1984.

Trump said that he still hopes that Kim would commit to a denuclearization plan but added that "we'll find out." 

The U.S. and North Korea are currently in a set of negotiations where sanctions against North Korea would be relieved if Pyongyang commits to a denuclearization plan. North Korea has set a year-end deadline for a deal to be reached, while accusing the U.S. of dragging its feet. 

Trump previously met Kim at the demilitarized zone between North and South Korea in June. 

North Korea is also not fond of joint military exercises between the U.S. and South Korea, viewing such drills as a preparation for an invasion and saying that they do not foster negotiations. 

Defense Secretary Mark Esper said in November that the U.S. would postpone the drills as an "act of goodwill" towards Pyongyang but North Korea would like them to be canceled entirely. 

In October, U.S. and North Korean negotiators met in Sweden but talks fell through on the first day of discussions. Trump and Kim have also met for negotiations in Vietnam and Singapore but failed to complete a deal.

Trump and Kim have an unusually strong relationship, with the two leaders sharing "beautiful letters" with one another and Trump calling Kim his friend. 

The situation hasn't always been so rosy between the two leaders, however. Trump in September 2017 called Kim "Little Rocket Man" in a derogatory way in front of the UN General Assembly, which prompted Kim to respond that Trump was "mentally deranged."