"That takes us a little while, as we amass everything and analyse it", Mattis said.
The comments come in the wake of yesterday's North Korean missile test.
"I believe it will further North Korea's isolation - diplomatic and economic isolation - because more and more nations are realising there's simply no collaboration with the global community".
South Korean President Moon Jae-in has scheduled a National Security Council meeting to discuss the launch.
Former top White House aide Steve Bannon told a reporter in August that there are no military solutions for North Korea. "The United Kingdom stands with the people of Japan in face of this bad, egregious, illegal, provocative, reckless act by the North Korean regime, which once again demonstrates their complete disregard for the sovereignty and the citizens of one of their neighbours", the British Ambassador to the UN, Matthew Rycroft told reporters after the meeting of the Security Council.
How has North Korea responded in the five weeks since President Donald Trump threated Pyongyang with "fire and fury?" Russian Federation is the largest employer of North Korean forced labor.
Tillerson noted that China, which supplies North Korea with most of its oil, and Russian Federation, as the largest employer of North Korean forced labor, have a unique responsibility in the diplomatic situation.More news: Rising Santa Fe closes two roads, I-75 being monitored
"If North Korea continues to walk down this path, it has no bright future".
U.S. Secretary of State Rex Tillerson also called for "new measures" against North Korea and said, "These continued provocations only deepen North Korea's diplomatic and economic isolation". North Korea has launched dozens of missiles under Kim Jong Un's leadership to accelerate a weapons programme created to give it the ability to target the United States with a powerful, nuclear-tipped missile. "China and Russian Federation must indicate their intolerance for these reckless missile launches by taking direct actions of their own", Tillerson said.
In the past two years, North Korea has conducted 27 ballistic missile launches and three nuclear tests.
"After seeing your capabilities and commitment here today, I am more confident than ever that our options in addressing this threat are both effective and overwhelming", Trump said inside an airplane hangar, surrounded by United States airmen and with a looming stealth bomber positioned behind him.
Experts have long questioned if the USA could indeed attack North Korea, given its ability to cause massive casualties south of the border. She expected a Trump call for maximum pressure on North Korea. Washington has tried to work with Beijing to restrain the latter's ally in Pyongyang through economic sanctions.