Bruce Bennett of the RAND Corporation think tank said Donald Trump needed to show the rogue state it would be able to respond to any attack with ease.
Speaking to CNBC, the expert said economic sanctions alone would not be enough to deter Kim Jong-un with fears rising over Pyongyang launching a “new kind of missile test”.
He said: “The US has got to be prepared to act very strongly in this case, not only with economic sanctions, it needs to take some form of military action.
“Maybe not an attack but a demonstration of some kind as well as some kind of political action against North Korea to really bring home to Kim Jong-un that we can cause him trouble if he causes us trouble.”
Mr Bennett said a combination of fleet deployments in the vicinity of North Korea and increased US assets on the ground in South Korea would send a strong message to Pyongyang.
He said: “By doing a combination of assets – ground, air and sea – that would be sending a very clear message that the US is committed.
“But we need to be careful that whatever we do, we’re also demonstrating, so I appreciate South Korea’s exercise with bombs today.”
The comments come after North Korea fired another missile into the Sea of Japan, sparking further fears Kim Jong-un could trigger World War 3.
South Korea’s military said Kim’s regime fired the “unidentified projectile” from Pyongyang towards the sea at 5:57am local time.
The Japanese government’s J-Alert warning system advised people in the area to take precautions.
Warnings were issued across Hokkaido, Aomori, Iwate, Miyagi, Akita, Yamagata, Fukushima, Ibaraki, Tochigi, Gunma, Niigata and Nagano.
But public broadcaster NHK said there was no sign of damage and the Japanese military did not attempt to shoot down the missile.
It passed over Japanese territory at around 6:06am local time before breaking into three pieces, officials in Tokyo said.
The latest missile launch follows ongoing tensions over North Korea’s refusal to end its nuclear weapons programme.