Haley also said she wanted to "tighten the screws" on North Korea, including stiffer sanctions and so-called secondary boycotts, in a joint press conference with Korean Ambassador to the UN Cho Tae-yul and Koro Bessho, Japanese Ambassador to the UN, to send a "strong, unified message to North Korea".
In another cyberattack suggesting possible Pyongyang involvement, a phishing attempt was made sometime before May 12 against a United Nations committee tasked with monitoring the implementation of sanctions against North Korea, a source confirmed Friday.
South Korean Ambassador Cho said it is "deeply regrettable" that North Korea launched a ballistic missile "only a few days after the inauguration of our new government in Seoul".
The May 14 launch was seen as a significant step forward in the North's weapons capabilities as it accelerates efforts to develop an intercontinental ballistic missile (ICBM) capable of delivering a nuclear warhead to the continental United States.
Thousands of citizens gathered on Thursday to cheer on the scientists over the successful launch of Hwasong 12, the medium-range missile fired on Sunday, the Korean Central News Agency (KCNA) said.
"People's enthusiastic welcome for defence science warriors", ran a front-page headline in the Rodong Sinmun newspaper, the official mouthpiece of the ruling Workers' Party, alongside pictures of the developers of what appears to be its longest-range ballistic missile.
"If this goes to a military solution it is going to be tragic on an unbelievable scale, and so our effort is to work with the United Nations, work with China, work with Japan, work with South Korea to try to find a way out of this situation", Mattis said at a news conference.
North Korea's latest launch came hours after Moon named his new foreign minister nominee and top advisers for security and foreign policy. "This system, last tested in February, has a shorter range than the missiles launched in North Korea's three most recent tests", the official said on condition of anonymity.
With an imputed range of 4,500 kilometres, the Hwasong-12 also puts USA bases on the Pacific island of Guam within reach.
Third, dialogue with North Korea is possible when the circumstances are right. This is not playtime.
North Korea called on South Korea to honour and fully implement previous inter-Korean agreements on cooperation and reconciliation.
Haley answered Putin and others who have made similar comments about the United States: "What about North Korea intimidating us?" -North Korea escalated earlier this year as North Korea conducted multiple missile launch tests while vowing to target the U.S.in order to combat what it calls American aggression.
If the United States "persists in anti-DPRK sanctions without understanding its rival, the (Trump) administration will have to take full responsibility for the ensuing catastrophic consequences", he warned.