Donald Trump. AP Photo/Evan Vucci

President Donald Trump attacked NBC News after the network reported on Wednesday that Trump called for a tenfold increase in the US's nuclear arsenal during a July 20 meeting at the Pentagon.

The request, which if acted on would violate decades of nuclear disarmament treaties and reverse longstanding US policy, reportedly came shortly before Secretary of State Rex Tillerson called the president a "moron."

"Fake @NBCNews made up a story that I wanted a 'tenfold' increase in our U.S. nuclear arsenal. Pure fiction, made up to demean. NBC = CNN!" Trump wrote.

The president suggested in another tweet that NBC should lose its broadcast license.

"With all of the Fake News coming out of NBC and the Networks, at what point is it appropriate to challenge their License? Bad for country!" he wrote.

Officials told NBC News that Trump was presented with a chart that illustrated the decline in the size of the US nuclear arsenal, which now includes 4,000 weapons, during the summer Pentagon meeting. After viewing the chart, Trump reportedly asked to grow the arsenal to 32,000, the number it reached at its peak in the 1960s.

NBC News reported that top White House aides as well as Cabinet and Pentagon officials were present at the meeting and that several were surprised by the president's apparent lack of understanding of a range of national security and military issues amid a standoff with nuclear-armed North Korea. NBC News first reported the "moron" comment last week, then linking it to a separate comment Trump apparently made about Afghanistan. The network first included the comments about nuclear arms in Wednesday's report.

The initial report about Tillerson's comment prompted Tillerson to confirm his commitment to the administration and compliment the president in an impromptu news conference. Trump said he believed the report of Tillerson's insult was "fake news" but nevertheless challenged Tillerson to an IQ test during an interview with Forbes published earlier this week.

"I think it's fake news," Trump told Forbes. "But if he did that, I guess we'll have to compare IQ tests."

"And I can tell you who is going to win," Trump said.

Arms-control experts maintain that an increase in US arms would spur another arms race with Russia and most likely China and could lead to other countries seeking nuclear capabilities.

But Trump has ordered the Pentagon to review its nuclear posture, with the US reassessing its nuclear assets in light of evolving threats. The most recent nuclear-posture review came in 2010 under President Barack Obama with the express goal of reducing weapons stockpiles.

Trump has voiced inconsistent opinions on the nuclear arsenal, at one point expressing a desire to "greatly strengthen and expand [US] nuclear capability" and in other instances insisting he does not think the arsenal should grow in size.

The country is embarking on a trillion-dollar modernization effort to update all three legs of its nuclear triad.

Alex Lockie contributed to this report.