The missile that North Korea fired over Japan overnight was a medium-range rocket that did not threaten US territory, the Pentagon has said.
"Initial assessment indicates the launch of an intermediate range ballistic missile (IRBM)," the Pentagon said in a statement.
"The North American Aerospace Defense Command determined this ballistic missile launch did not pose a threat to North America. US Pacific Command determined this ballistic missile launch did not pose a threat to Guam," it said.
Earlier, US President Donald Trump has warned that "all options" remained under consideration following the launch.
"Threatening and destabilising actions only increase the North Korean regime's isolation in the region and among all nations of the world," the White House said in a statement.
"All options are on the table."
The statement said that the world "has received North Korea's latest message loud and clear: this regime has signaled its contempt for its neighbours, for all members of the United Nations, and for minimum standards of acceptable international behavior."
The statement reiterates Mr Trump's past threats to use military action to resolve the ongoing crisis with North Korea.
Mr Trump also spoke by phone with Japanese Prime Minister Shinzo Abe following the missile launch.
"The two leaders agreed that North Korea poses a grave and growing direct threat to the United States, Japan, and the Republic of Korea, as well as to countries around the world," the White House said in a separate statement.
"President Trump and Prime Minister Abe committed to increasing pressure on North Korea, and doing their utmost to convince the international community to do the same."
United States Ambassador to the United Nations Nikki Haley said the launch of a missile over Japan was "absolutely unacceptable and irresponsible" and that the Security Council now needed to take serious action.
"No country should have missiles flying over them like those 130 million people in Japan. It's unacceptable," she told reporters.
North Korea has "violated every single UN Security Council resolution that we've had and so I think something serious has to happen," Ms Haley added.
China also warned that tensions on the Korean peninsula have reached "tipping point", but said the United States and South Korea are partly to blame.
Foreign ministry spokeswoman Hua Chunying urged all sides to avoid provocations and repeated China's call for the North to suspend missile tests in return for a halt to US-South Korean military exercises.
The situation is "now at a tipping point approaching a crisis. At the same time there is an opportunity to reopen peace talks," Ms Hua told a news briefing.
Russia said it is "extremely worried" about the situation in North Korea, hitting out at a "tendency towards an escalation".
"We see a tendency towards an escalation ... and we are extremely concerned by the general developments," Russia's deputy foreign minister Sergei Ryabkov was quoted as saying by RIA Novosti state news agency.
Sirens blared out early this morning and text messages were fired off across the north of Japan, warning people in the missile's flightpath to take cover.
Japan said the missile overflew Hokkaido, Japan's northernmost island, with Prime Minister Shinzo Abe describing it as "an unprecedented, serious and grave threat" to regional security.
The test, one of the most provocative ever from the reclusive state, appeared to have been of a recently developed intermediate-range Hwasong-12 missile, experts said.
North Korea's ambassador to the United Nations in Geneva has defended his country's use of "tough counter-measures" against what he said was US aggression.
Addressing the UN Conference on Disarmament in Geneva, Han Tae-Song said avoided any direct mention of the rocket that flew over Japan and triggered global alarm.
He said: "Now that the US has openly declared its hostile intention towards DPR Korea by raising joint aggressive military exercises despite repeated warnings... my country has every reason to respond with tough counter-measures as an exercise of its rights to self-defence."
He said the US would be responsible for "the catastrophic consequences" that may result from heightened tensions on the Korean Peninsula.
The European Union's top diplomat condemned the missile launch, offering the bloc's support for any future talks but also warning of possible steps following meetings at the United Nations Security Council.
"We fully support calls for an emergency meeting of the UN Security Council today," the EU's foreign policy chief Federica Mogherini said in a statement, saying the European Union will look at an "appropriate response in close consultation with key partners and in line with UN Security Council deliberations."
The European Union last toughened its economic sanctions on North Korea on 10 August.
Meanwhile, British Prime Minister Theresa May is outraged by North Korea's "reckless provocation" in carrying out the tests, her spokeswoman has said.
She told reporters: "The prime minister is outraged by North Korea's reckless provocation and she strongly condemns these illegal tests. From our perspective we will need to continue to work with our international partners to keep the pressure on North Korea."
Mrs May is travelling to Japan later today and will have talks with Japanese Prime Minister Shinzo Abe.
Earlier this month, North Korea threatened to fire four Hwasong-12 missiles into the sea near the US Pacific territory of Guam after US President Donald Trump warned North Korea would face "fire and fury" if it threatened the US.
North Korea has conducted dozens of ballistic missile tests under young leader Kim Jong-un, the most recent on Saturday, but firing projectiles over mainland Japan is rare.
"North Korea's reckless action is an unprecedented, serious and a grave threat to our nation," Mr Abe told reporters.
He said he spoke to Mr Trump and they agreed to increase pressure on North Korea.
Mr Trump also said the United States was "100% with Japan", Mr Abe told reporters.
The United Nations Security Council will meet later today to discuss the test, diplomats said.
Earlier this month, the 15-member Security Council unanimously imposed new sanctions on North Korea in response to two long-range missile launches in July.
Mr Ryabkov said the huge joint military drills between South Korea and the United States, which began on 21 August, "had played their role in provoking Pyongyang into this new firing".
Tens of thousands of troops are participating in the two-week "Ulchi Freedom Guardian" exercise on the Korean Peninsula in a move which the North views as highly provocative, seeing it as a rehearsal for an invasion.
