The United States has strongly condemned North Korea's "provocative" launch of several missiles that posed no immediate threat to US territory but warranted a diplomatic counter-offensive.
"The United States strongly condemns these missile launches... We are consulting with international partners on next steps," White House Press Secretary Tony Snow said on Tuesday night in a statement.
He said Pyongyang's actions appear to indicate it "has not yet made the strategic decision to give up their nuclear programmes ... Accordingly, we will continue to take all necessary measures to protect ourselves and our allies."
Senior US officials immediately reached out to their counterparts in China, Japan, Russia and South Korea -- US partners in six-nation talks on Pyongyang's nuclear ambitions -- and were weighing an array of diplomatic options.
US Secretary of State Condoleezza Rice was hitting the phones to sound out her counterparts and Washington spearheaded a round of urgent consultations at the United Nations, where a Security Council meeting was scheduled on Wednesday.
The senior US envoy for North Korean issues, Assistant Secretary of State Christopher Hill, was preparing to leave for the region on Wednesday, while South Korea's national security adviser was due at the White House.
"You're going to see a lot of diplomatic activity in Washington over the next 24-48 hours," White House national security adviser Stephen Hadley told reporters on a conference call.
US officials said the North Korean missile salvo included a long-range Taepodong 2 thought to be able to reach the United States but that it failed less than a minute into flight and was thought to have crashed, like the others, in the Sea of Japan.