Pentagon chief Jim Mattis delivered a somber caution on North Korea on Friday, saying any military attempts to resolve the crisis would be "tragic on an unbelievable scale."
Mattis was speaking to reporters at the Pentagon days after North Korea test-fired what analysts say was its longest-range rocket yet.
Despite tough talk from top US officials in recent weeks and the deployment of an aircraft carrier strike group to the region, Mattis said the best option for North Korea is finding an international solution to effectively apply pressure on Pyongyang.
"As you know, if this goes to a military solution, it is going to be tragic on an unbelievable scale, and so our effort is to work with the UN, work with China, work with Japan, work with South Korea to try to find a way out of this situation," he said.
Pyongyang is accelerating efforts to develop an intercontinental ballistic missile (ICBM) capable of delivering a nuclear warhead to the continental United States.
Though Mattis said Pyongyang isn't listening to cautions from the international community, he credited China's efforts to apply pressure as having some limited influence.
"There appears to be some impact by the Chinese working here," he said.
Mattis said the rocket tested Sunday had gone very high and North Korean scientists likely learned a lot from the test, but he would not say if it was clear the missile made a controlled re-entry from outside the atmosphere.
In Pyongyang on Friday, thousands of residents lined the streets to give the scientists and workers behind Sunday's missile test a hero's welcome, state media reported.
Even without its missiles, North Korea has amassed artillery units along its border with South Korea and any military action from Pyongyang could be devastating.
The capital, Seoul, is only about 35 miles (55 kilometers) away and some of the North's canons could rain shells onto the city of 10 million.