President Trump commended the Pentagon on Friday for fulfilling a request he made at the outset of his administration for an updated report on the U.S. nuclear arsenal, something that hasn't been done since 2010.

"In one of my first acts in office, I directed Secretary of Defense Jim Mattis to conduct a Nuclear Posture Review," Trump said in a statement. "After a year of thoughtful analysis and careful deliberations across our government, today, my administration is announcing the conclusions of this review."

The review, released Friday, outlines a series of new steps the U.S. should take to ensure its nuclear capabilities match those of Russia and China, both of which have made significant efforts to increase their warhead inventories.

"We must look reality in the eye and see the world as it is, not as we wish it to be," Mattis wrote in a summary of the classified review, adding that the U.S. should pursue a "lower-yield" option for missiles that are currently launched from submarines. Such missiles would produce less casualties in their target areas.

"Expanding flexible U.S. nuclear options now, to include lower-yield options, is important for the preservation of credible deterrence against regional aggression," Mattis said.

Trump said Friday his administration is actively taking steps to complete a "much-needed modernization of our nuclear weapons, infrastructure and delivery systems," while criticizing his predecessors for failing to do so.

"Over the past decade, despite U.S. efforts to reduce the roles and numbers of nuclear weapons, other nuclear nations grew their stockpiles, increased their prominence of nuclear weapons in their security strategies, and — in some cases — pursued the development of new nuclear capabilities to threaten other nations," he said.

The 2018 NPR report "develops capabilities aimed at making use of nuclear weapons less likely," Trump added. "And, importantly, it reaffirms our commitment to arms control and nuclear non-proliferation, maintains the moratorium on nuclear testing, and commits to improving efforts to prevent, detect, and respond to nuclear terrorism."

Friday's report comes as the Trump administration continues to weigh a range of military options against North Korea, which has refused to cease its nuclear program despite mounting international pressure.