President Trump announced new investments in missile defenses aimed at shielding the nation against growing threats from North Korea, China, Russia and Iran.

“Our goal is simple: to ensure that we can detect and destroy any missile launched against the United States anywhere, any time, any place,” Mr. Trump said at the Pentagon.

Background: Antimissile systems are extremely costly — the U.S. has spent over $300 billion on them to date — and also extremely difficult to get right. It has proved challenging to intercept speeding targets in the sky: A system introduced in 2004 has failed in 50 percent of tests.

Timing: The announcement came a day before Vice President Mike Pence is scheduled to meet with North Korea’s lead nuclear program negotiator, Kim Yong-chol, in Washington. Earlier this week, Mr. Pence said the U.S. was still waiting for “concrete steps from North Korea” toward denuclearization — a demand that has so far stalled dialogue between the two countries.