The Army's top officer said Tuesday that Defense Secretary Jim Mattis has clearly tasked the service with being prepared for war with North Korea.

Gen. Mark Milley, the chief of staff, said the U.S. is still seeking a peaceful diplomatic solution to the crisis over the North's nuclear missile program, but he told the Association of the U.S. Army conference that Mattis had meant what he said when he warned soldiers "you have got to be ready" during a keynote at the same event Monday.

"Secretary Mattis just yesterday very clearly tasked the United States Army to be ready. His words were carefully chosen," Milley said. "So our No. 1 task, bar none, remains readiness. Readiness for what? It's readiness for war."

Mattis said during his speech Monday that the international community has already condemned North Korea with two United Nations Security Council votes imposing new sanctions.

"There's one thing the U.S. Army can do, and that is, you have got to be ready to ensure that we have military options that our president can employ, if needed," he said.

U.S. diplomatic efforts are being led by Secretary of State Rex Tillerson, who said he was open to new dialogue with the regime to head off its quest for a nuclear intercontinental ballistic missile capable of hitting American cities despite sanctions and international condemnation. But President Trump has said talking with the North might be a waste of time and hinted at the use of military force if Pyongyang does not abandon its nuclear aspirations.

"No one in this room knows with certainty how this situation will play out and someone in this room will be making the critical decisions," Milley said. "But you can be sure that decisions will be made one way or the other because of the rapid pace of North Korea's ICBM and nuclear weapons development."

Milley said "no one wants a war" and detailed the grave consequences if the United States and North Korea do fall into conflict.

"All recognize that a war on the Korean Peninsula would be a tragedy on a huge scale with intense levels of violence in dense urban areas, enormous damage to infrastructure, and economic effects felt worldwide," he said. "Most importantly there would be significant loss of human life, a level of war on a scale that few in the world today have ever seen."