Meanwhile, three US aircraft carriers - the USS Ronald Reagan, USS Theodore Roosevelt and USS Nimitz - sailed off the Korean Peninsula on Monday in a massive show of force against Kim Jong Un's regime as part four days of drills that end Tuesday.
"That might be a odd thing to happen but it's a possibility", he said.
It is the first such United States triple-carrier drill in the region for a decade.
According to the U.S. Navy, it is the first three-carrier exercise in the Western Pacific since 2007. "The problem is that South Korea is blindly following the US which is intent on the scheme for a nuclear war".More news: West Indies tour to Pakistan moved to next March
Tensions between North Korea and the USA have escalated in recent months following the rogue state's sixth nuclear bomb test on September 3, which earned more sanctions and condemnations from the UN.
Trump will fly to Manilla on Sunday afternoon for the Association of Southeast Asian Nations (ASEAN) meetings and East Asia Summit, which will both be comprised of leaders from Southeast Asian nations and representatives from dialogue countries. The weapons you're acquiring are not making you safer, they are putting your regime in grave danger.
He also said the U.S.is maintaining "a surprise strike posture with frequent flight of B-1B and B-2 formations to the airspace of South Korea".
But Pyongyang doesn't seem interested in negotating.More news: Arab League To Meet On Iran at Saudi Request
Trump followed up his freakish tweet by telling reporters that it would be a "good thing" for him and dictator to become friends.
The president responded sarcastically in a tweet Saturday, writing, "Why would Kim Jong-un insult me by calling me 'old, ' when I would NEVER call him 'short and fat?' Oh well, I try so hard to be his friend - and maybe someday that will happen!"
Asked at news conference with Vietnam's president later Sunday if he could become friends with the North Korean leader, Trump replied it "might be a unusual thing to happen but it's certainly a possibility".
Trump signed an executive order in September slapping new travel and economic sanctions on North Korea, as the administration seeks to pressure Kim Jong Un in a showdown over the North Korean leader's nuclear program.More news: Teenage Mutant Ninja Turtles Are Injustice 2 DLC