“If you violate international agreements, if you fail to live up to commitments, if you become a threat to others, at some point a response is likely to be undertaken,” Tillerson told ABC’s This Week.

There was little doubt the missile strikes would be seen in Pyongyang as a message. The North has long claimed that the U.S. is preparing some kind of assault against it and justifies its nuclear weapons as defensive in nature.

U.S. Navy ships are a common presence in the Korean Peninsula region and serve in part as a show of force. On Saturday night, the Pentagon said a Navy carrier strike group was moving toward the western Pacific Ocean to provide more of a physical presence in the region.

Tillerson Cites Russian Inaction as Helping to Fuel Syrian Poison Gas Attack

North Korea has pledged to bolster its defenses to protect against such airstrikes. The North called the U.S. action in Syria “absolutely unpardonable” and said it proves that its nuclear weapons are justified to protect the country against Washington’s “evermore reckless moves for a war.”

The comments were made by a Foreign Ministry official and carried by North Korea’s state-run Korean Central News Agency on Sunday. The report did not name the official, which is common in KCNA reports.

In appearances on the Sunday news shows, Tillerson said advances in North Korea’s ballistic missile program concerned the U.S. the most. Asked on ABC if development of an intercontinental missile was a “red line” for Trump, Tillerson said: “If we judge that they have perfected that type of delivery system, then that becomes a very serious stage of their further development.”

Russia Drone May Have Been Near Syria Gas Attack

The missile strikes against Syria’s Assad-led government took place Thursday night as President Donald Trump hosted Chinese President Xi Jinping for dinner at Trump’s Florida estate. Among the topics of discussion was the vexing problem of North Korea.

“I think there’s a shared view and no disagreement as to how dangerous the situation has become,” Tillerson said on CBS’ Face the Nation. “And I think even China is beginning to recognize that this presents a threat … to China’s interests as well.”

Trump and South Korea’s leader, acting President Hwang Kyo-Ahn, spoke by phone on Friday, according to the White House, which said they agreed to stay in close contact about North Korea and other issues.

Trump has said China, with its ties to North Korea, should deal with its neighbor, but that the U.S. was prepared to act on its own if necessary.