Early Tuesday morning, North Korea fired an intermediate range ballistic missile over Japan's northern Hokkaido island. It broke up shortly afterwards over the western Pacific Ocean.

With this provocation, North Korean tyrant Kim Jong Un has blunted American optimism that he might be willing to trim his ballistic saber rattling. It is clear that further U.S. action is required to force him into constructive diplomacy. The time has come for the Trump administration to take action.

An invasion of North Korea would entail an immense loss of life and is clearly not on the cards. But there are measures a long way short of such hostilities that could prove effective and which President Trump should now employ. He should issue a clear statement of policy that the U.S. military will from now on shoot down North Korean intermediate or intercontinental ballistic missiles if Kim launches them in a way that poses a threat to America and its allies.

Trump should first affirm that he will unilaterally shoot down missiles threatening U.S. territories. But he should also seek an agreement with Prime Minister Shinzo Abe of Japan towards joint action. If a bilateral agreement were to be reached, it would attract diplomatic support from the European Union and other powers. This is important in establishing a new international norm, that ballistic missile aggression will not be tolerated.

How does one define a launch that is "threatening," a threshold that would justify downing a North Korean missile? The definition should apply to any launch which puts the missile on a course that would transit or strike a U.S. ally, or come within 700 miles of an American territory such as Guam. This would exclude the destruction of short-range missiles or missiles on their launchpads, which could invite international suggestions that the U.S. was escalating conflict. At the same time, however, it would be sufficient to secure American interests and send an unmistakable message of resolve and demonstrate technical capabilites that should make Kim pause.

There is still further utility to this new approach beyond the defense of the U.S. and its allies. By eliminating North Korean ballistic missiles at their mid-course or terminal phases, the U.S. would deny North Korea the technical data they need to perfect their missile program. North Korea's ballistic missile program remains in its late developmental stage, and its scientists need data from each test to eliminate weaknesses. By destroying Kim's missiles, the U.S. would reduce his data returns and impose expensive losses on his capital investment project.

This shoot-down policy would also help perfect our ballistic missile defense capabilities. Whether confronting North Korea or other states such as Iran, the U.S. needs to develop reliable missile defenses. As it navigate an era of escalating ballistic missile proliferation, America needs credible missile deterrence.

There are additional, broader strategic benefits to a shoot-down policy. It will encourage Kim and China to realize that the former cannot out-escalate the United States military. Absent that understanding, China will continue to run out the clock until North Korea can strike U.S. cities with nuclear weapons. By employing military force against North Korea, but in a proportionate way, Trump would bring that nation and its Chinese patron down to earth and puncture the myth that his threat to use force is a bluff. This matters not for the sake of war, but for the cause of peace.

There is a diplomatic solution to this crisis, but it will only succeed if China believes the alternative is U.S. military action against North Korea. So far, that option remains as impractical as it is unacceptable. But if the U.S. doesn't act fast, it might become unavoidable.