President Donald Trump on Thursday called for investments in space-based sensors to detect and track enemy missiles as part of a new U.S. missile defense strategy.

The Missile Defense Review singled out concerns about advancing capabilities by China, Russia, North Korea and Iran. But Trump did not refer to North Korea, apparently taking into consideration a likely second summit with the North's leader Kim Jong Un.

Calling outer space "a new war fighting domain," Trump suggested space-based sensors are intended to counter hypersonic technology and missiles, an area in which China has been making major progress.

In his remarks at the Pentagon, Trump also pushed for the introduction of 20 new ground-based interceptors at Fort Greely, Alaska.

The president said that in the past, the United States lacked a comprehensive missile defense strategy that extends beyond ballistic missiles.

"Under our plan, that will change," he said. "The U.S. will now adjust its posture to also defend against any missile strikes to include cruise and hypersonic missiles."

On North Korea, the review said, "While a possible new avenue to peace now exists with North Korea, it continues to pose an extraordinary threat and the United States must remain vigilant."

In lieu of a reference to North Korea in Trump's remarks, acting Defense Secretary Patrick Shanahan acknowledged Pyongyang's missile threat.

"While we are forging a new path to peace on the Korean Peninsula, North Korea's missiles remain a significant concern, so do Iran's," Shanahan said.