— -- After North Korea announced on Sunday that it successfully conducted a test of an extraordinarily powerful hydrogen bomb meant to be loaded onto an intercontinental ballistic missile, President Donald Trump said "we'll see" about a possible attack on the country.
A newsreader for North Korean state-run television announced the test early Sunday, saying it was ordered by Kim Jong Un. The broadcaster called it a "complete success," adding that the "two-stage thermonuclear weapon" had "unprecedented" strength.
This latest test was the most powerful of North Korea's six nuclear tests so far.
US, Trump respond to reports of test
Treasury Secretary Steve Mnuchin announced Sunday morning that he will be drafting a sanctions package against North Korea that could go so far as to cut off all U.S. trade with any country that does business with North Korea.
"It's clear that this behavior is completely unacceptable," he said of the test on "Fox News Sunday." "We've already started with sanctions against North Korea, but I'm going to start a sanctions package to send to the president, for his strong consideration, that anybody that wants to do trade or business with them would be prevented from doing trade or business with us."
Mnuchin added that the U.S. will work with allies and China as it takes steps to more forcefully cut off North Korea from the global economy.
He said he spoke to Trump after the test took place.
Trump first responded to the reported test on Twitter before Mnuchin's warning, commenting on North Korea's continuing "hostile and dangerous" actions toward the U.S. and its being a "great threat and embarrassment to China." The president also said South Korea's "talk of appeasement" with its northern neighbor won't work.
Asked later in the day whether the U.S. will attack North Korea, Trump, who was attending a service at St. John's Episcopal Church in Washington, said, "We'll see."
He returned to the subject of North Korea on Twitter later in the day, promising that he will meet with Defense Secretary James Mattis, White House chief of staff John Kelly and "other military leaders" to discuss America's policy toward North Korea.
Trump backed up Mnuchin's words, saying the U.S. will consider "stopping all trade with any country doing business with North Korea."
Mattis delivered a brief statement to reporters outside the White House on Sunday afternoon, warning, "Any threat to the United States or its territories, including Guam, or our allies will be met with a massive military response," he said. "A response both effective and overwhelming. Kim Jong Un should take heed of the United States Security Council's unified voice. All members unanimously agreed on the threat North Korea poses and remain unanimous in their commitment to the denuclearization of the Korean Peninsula."
"Because we are not looking to the total annihilation of a country, namely North Korea, but as I said, we have many options to do so," he went on to say.
Reports of seismic activity
North Korea's announcement of the test came a few hours after a 6.3-magnitude explosion was detected in North Korea at 12:29 p.m. local time Sunday, according to the United States Geological Survey.
According to the USGS, the seismic activity occurred 24 kilometers east-northeast of Sungjibaegam, North Korea. "Possible explosion, located near the site where North Korea has detonated nuclear explosions in the past," read a statement on the USGS website, before confirmation that it was a nuclear test.
The USGS said that a second, 4.1-magnitude seismic event occurred 22 kilometers east-northeast of Sungjibaegam. "Seismic event collocated with the larger possible explosion 8 minutes and 32 seconds earlier," read a statement on the agency's website. "This significantly smaller event is likely a secondary feature (possibly a structural collapse) associated with the larger event."
U.S. national security adviser H.R. McMaster spoke with Chung Eui-yong, his counterpart at South Korea's National Security Office, for 20 minutes in an emergency phone call after the test, according to the South Korean presidential office.
Chung said Sunday that South Korean President Moon Jae-in will seek every available diplomatic measure, including new sanctions from the United Nations Security Council. Chung said Moon will also discuss with the Trump administration ways to deploy the "strongest strategic assets" the U.S. has.
At a press conference Sunday at the South Korean Ministry of Defense, Cho Han-kyu, the director general of operations with the Joint Chiefs of Staff, said the military "strongly condemns North Korea in conducting ICBM-level missile launches and nuclear tests, even stronger than those conducted in the past, regardless of our government's suggestions to ease military tension and bring peace to the Korean Peninsula."
Cho added, "The South Korea–U.S. alliance, in closest cooperation ever, has all the capability to punish North Korea, and we will show our action demonstrating a strong response of the South Korea–U.S. combined forces [against North Korea]."
UN secretary-general, countries around the world weigh in
U.N. Secretary General Antonio Guterres released a statement about the test through a spokesperson that singled out North Korea as the "only country that continues to break the norm against nuclear test explosions."
"This act is yet another serious breach of the [Democratic People's Republic of Korea's] international obligations and undermines international nonproliferation and disarmament efforts," the statement read. "This act is also profoundly destabilizing for regional security."
On Sunday afternoon U.S. Ambassador to the U.N. Nikki Haley said that an open emergency U.N. Security Council meeting will take place on Monday morning.
Condemnation of the test came from China, Russia and France as well.
China's Ministry of Foreign Affairs said in a statement, "The Democratic People's Republic of Korea has once again conducted a nuclear test in spite of widespread opposition from the international community. The Chinese government resolutely opposes and strongly condemns it."
The Russian Foreign Ministry said in a statement Sunday that North Korea's nuclear test "deserves absolute condemnation," adding that immediate dialogue and negotiations are necessary. It says that's the only way settle the Korean Peninsula's problems, "including the nuclear problem."
The statement continued, "This yet another example of Pyongyang's outright disregard of the demands of respective U.N. Security Council resolutions and international law deserves absolute condemnation."
The ministry said Russia is willing to participate in negotiations, "including in the context of the implementing of the Russian-Chinese road map."
French President Emmanuel Macron said in a statement that he "calls on the members of the United Nations Security Council to quickly react to this new violation by North Korea of international law."
He continued, "The international community must treat this new provocation with the utmost firmness, in order to bring North Korea to come back unconditionally to the path of dialogue and to proceed to the complete, verifiable and irreversible dismantling of its nuclear and ballistic program."
South Korea's weather agency, the Korea Meteorological Administration, said on Sunday that the apparent nuclear test appears to have been significantly stronger than the North's previous tests.
The agency estimated that the nuclear blast yield of the presumed test was 50 to 60 kilotons, or five to six times as strong as North Korea's fifth test, conducted in September 2016.
Before North Korea's announcement, Japan confirmed that the rogue nation conducted a nuclear test. "It is absolutely unacceptable if North Korea did force another nuclear test, and we must protest strongly," Prime Minister Shinzo Abe said.
And South Korea's Joint Chiefs of Staff also presumed that North Korea conducted a sixth nuclear test before the North made the announcement. When news broke of the seismic activity, South Korea's Joint Chiefs of Staff said the seismic activity was artificial.
South Korea's presidential office said it will hold a National Security Council meeting chaired by Moon.
The North Korean government released photos earlier Sunday of Kim talking with his lieutenants as he watched a silver, peanut-shaped device that was apparently the purported thermonuclear weapon destined for an ICBM. What appeared to be the nose cone of a missile could also be seen near the alleged bomb in one picture. The photo could not be independently verified. Another photo showed a diagram on the wall of a bomb mounted inside a cone.
ABC News' Christopher Donato, Michael O'Keefe, Dragana Jovanovic, Jordyn Phelps and Joohee Cho contributed to this report.