Kim Jong-Un, leader of the secluded country, has repeatedly declared his ambition to build an intercontinental ballistic missile that could strike the United States. Photograph: (AFP)
US Ambassador Nikki Haley's scathing comment comes after Pyongyang defied UN decree to test-fire missiles on March 6
The United States disagreed with China that it should hold talks with North Korea because their leader Kinm Jong-Un was "not rational".
China had earlier asked the US and North Korea to avert a "head-on collision" by holding talks to smoothen the latest flare-up between the countries.
Beijing, North Korea's trusted ally, had earlier asked Pyongyang to junk its nuclear development and wanted the US to put hold up the annual US-South Korean military drills
But the US rebuffed China's entreaties on Wednesday, with their ambassador Nikki Haley putting out a withering a criticism of the North leader following a closed-door meeting of the UN Security Council.
"We are not dealing with a rational person," the ambassador said, adding that Kim is a person "who has not had rational acts, who is not thinking clearly".
North Korea fired at least four missiles toward Japan on Monday, three of which splashed down in waters near Japan.
The US ambassador said "all the options are on the table" and did not rule out talks completely but she made clear that the onus was on North Korea to show a willingness to seek a diplomatic solution.
"We have to see some sort of positive action taken by North Korea before we can ever take them seriously," said Haley.
China, Pyongyang's main ally, earlier called on North Korea to suspend its nuclear and missile activities in exchange for the US and South Korea halting joint military exercises in South Korea.
The proposal from the Chinese foreign minister however appeared to fall flat, with Britain, France and Japan saying that North Korea must take the first step to show that it was ready to change course and abandon its military and nuclear programs.
Chinese Ambassador Liu Jieyi stressed the importance of reducing tensions on the Korean peninsula, telling reporters after the meeting that this must be done "in a negotiated way".
The council has imposed six sets of sanctions on North Korea -- two of which were adopted last year to significantly ramp up measures and deny Kim's regime hard currency revenue.
(WION with inputs from AFP)