The top defense official suggested military action "would lead to severe consequences", and he said the USA military is ready to support its Japanese and South Korean allies.
Even a so-called surgical strike aimed at North Korea's partially hidden nuclear and missile force is unlikely to destroy the arsenal or stop its leader, Kim Jong Un, from swiftly retaliating with long-range artillery that could kill stunning numbers in South Korea within minutes.
Earlier Thursday in Hamburg, Trump met with Moon and Japanese Prime Minister Shinzo Abe on North Korea's test launch Tuesday of a missile that was first classified by the USA military as an IRBM, or Intermediate Range Ballistic Missile, and then later classified as an Intercontinental Ballistic Missile.
The Trump administration has tried to be more forceful on North Korea than the Obama administration, and Tillerson described this approach Friday as a "peaceful pressure campaign".
US President Donald Trump said he was considering some "very severe things" to respond to North Korea's test launch, calling the country's behaviour "a shame". Trump stopped in Poland on his way to the G20 summit in Germany.
When asked about imminent military action against Pyongyang, Trump said, "As far as North Korea is concerned, I don't know". But he would not draw red lines and would not reveal exactly what he was planning, he said.
This, they said, is a major escalation that directly violates multiple UNSC resolutions and that clearly demonstrates the growing threat the North Korea poses to the United States, South Korea, and Japan, as well as other countries around the world, the joint statement said.
Chinese Foreign Ministry spokesman Geng Shuang, speaking in Beijing earlier on Thursday, said China fully implemented United Nations resolutions on North Korea.
The ambassador added: "One of our capabilities lies with our considerable military forces".
Woolsey is not alone in fearing the impact of the president's tweeting.
North Korea hit back Thursday, with its propaganda National Peace Committee for Korea criticising Moon for denouncing Pyongyang "instead of getting rejoiced over the praiseworthy event" staged by its northern neighbour, according to the KCNA news agency.
"I don't like him saying that he wants to meet Kim Jong Un and that that 'would be an honor, '" he said.
"Something has to be done", the president also said. There is no sound military option. "That includes Russian Federation and China and this is now a global problem", Foreign Minister Julie Bishop said. "Get Russia's help. Try something new".
Zhang Tuosheng, director of the Center for Foreign Policy Studies at the China Foundation for global and Strategic Studies, said at the meeting that China can not afford the risks of military confrontation.