Lee told his USA counterpart General Joseph Dunford and Japanese counterpart Admiral Katsutoshi Kawano that North Korea's nuclear and missile programs are becoming a serious threat not only for the Korean Peninsula but also the worldwide community.
John Schilling, a missile expert contributing to Washington's 38 North think tank, estimated it would take until at least 2020 for North Korea to be able to develop an ICBM capable of reaching the U.S. mainland and until 2025 for one powered by solid fuel.
It's moving ahead with its nuclear weapons program as well. "He also said the situation had become overheated, and had suggested the importance of an intermediary".
South Korea held a National Security Council meeting after the launch, which its Foreign Ministry said "throws cold water" on efforts to ease tensions on the peninsula.
North Korea conducted two nuclear tests previous year.More news: Trump 'hopeful' of brokering Middle-east peace deal
South Korea's Joint Chiefs of Staff said in a statement that the South Korean military bolstered its air surveillance and broadcast a warning to North Korea in response to the object.
Its state media, meanwhile, have stepped up their calls for even more missile launches because of what the government says is an increasingly hostile policy from President Trump.
US President Donald Trump has warned of a potential "major, major conflict" with North Korea over its weapons programs. "This is the DPRK's answer to the Trump administration'".
The DPRK refers to the abbreviation of North Korea's full name - the Democratic People's Republic of Korea.
In an interview with "Fox News Sunday", U.S. Secretary of State Rex Tillerson said the ongoing testing is "disappointing" and "disturbing".More news: Rocco Forte Open: Alvaro Quiros beats Zander Lombard at second play-off hole
The statement came a day after the UNSC released a unanimously-backed statement, strongly censuring North Korea's latest missile test and urging the UN's sanction committee to boost efforts towards implementing the sanctions imposed on Pyongyang.
North Korea said that launch tested the capability to carry a "large-size heavy nuclear warhead" and put the USA mainland within "sighting range".
Experts said that rocket flew higher and for a longer time than any other missile previously tested by North Korea and represents another big advance toward a viable ICBM.
"Saying with pride that the missile's rate of hits is very accurate and Pukguksong-2 is a successful strategic weapon, he (Kim) approved the deployment of this weapon system for action", KCNA said.
Solid fuel missiles can be fired far more rapidly, dramatically shortening the time available for any attempt to intervene and prevent a launch.More news: Israeli settler set free after killing Palestinian
So far nearly all the North's missiles have been liquid-fuelled, which have to be time-consumingly filled with propellant before launch. That makes them easier to spot and easier to destroy.