Secretary of State Rex Tillerson has been at odds with White House officials for small issues including some of Tillerson's habits, according to a report Wednesday.

Aides to Tillerson, who rejected claims Wednesday that he had called President Trump a "moron," have clashed with White House officials over him not returning phone calls, the Washington Post reported.

This small quibble with Tillerson, noted by unnamed White House officials, comes along with larger issues too, including U.S. policy in Afghanistan and how to negotiate with a nuclear-armed North Korea. Trump tweeted over the weekend that Tillerson was "wasting his time trying to negotiate with Little Rocket Man," in reference to North Korea's Leader Kim Jong Un.

After the report from NBC News Wednesday morning about tensions between Tillerson and Trump, the president called it a "totally phony story" and Tillerson publicly affirmed his support of Trump.

"Let me tell you what I've learned about this president, whom I did not know before taking this office," Tillerson said. "He loves his country. He puts Americans and America first. He's smart. He demands results wherever he goes, and he holds those around him accountable for whether they've done the job he's asked them to do. Accountability is one of the bedrock values the president and I share."