Trump convened a White House meeting Sunday afternoon of military leaders, his national security team and Vice President Mike Pence, where Mattis said they reviewed each of the United States' military options in the Asia-Pacific.
"We have many military options, and the President wanted to be briefed on each one of them", he said.
But the U.S. does have the forces such as the THAAD and Aegis missile defense systems in place to protect South Korea and Japan from a North Korean first strike, Hertling said.
After concluding his statement, Mattis walked away as reporters shouted follow up questions, refusing to confirm whether he believes North Korea can mount a nuclear warhead on a missile, whether it was, indeed, a hydrogen bomb, or if President Trump intends to go to war with Pyongyang.
North Korea, in a broadcast on its state-run television network, confirmed it has successfully conducted tested a hydrogen bomb meant for intercontinental ballistic missiles, several media outlets reported Sunday. "It is of course right to say that all options are on the table, but we really don't see an easy military solution", he said.
South Korean officials watch news broadcasts showing North Korea's leader Kim Jong-Un, at the Korea Meteorological Administration in Seoul on September 3, 2017.
The global community roundly condemned the Kim regime's latest weapons test. It was the sixth nuclear test conducted by the communist nation, but the first to occur since Trump took office.
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Putin also spoke by phone with Japanese Prime Minister Shinzo Abe, who called for an emergency session of the United Nations Security Council to discuss stricter sanctions against the Kim regime. Earlier on Sunday, the president issued a series of tweets commenting on Pyongyang's sixth test.
Boris Johnson, the British Foreign Secretary, said North Korea had the power to "vaporise" large parts of the population of South Korea even without nuclear weapons. "North Korea is a rogue nation which has become a great threat and embarrassment to China, which is trying to help but with little success", Trump tweeted.
Mattis continued to address the aggression displayed by North Korean dictator Kim Jong-un, saying that he should "take heed" of the UN's Security Council's unanimous position against North Korea's nuclear program.
An H-bomb, also known as a thermonuclear device, would be immeasurably more destructive.
South Korea's "talk of appeasement" with North Korea will not work, Trump said, adding that Pyongyang will "only understand one thing".
It has always been accepted that North Korea has intercontinental ballistic missiles (ICBMs) capable of reaching the mainland of the United States.
The United States has already imposed economic sanctions on North Korea to stop the country's pursuit on a nuclear weapon, including tests on inter-continental missiles on which to attach a nuclear warhead.