US Secretary of State Rex Tillerson said on Wednesday he had never considered resigning and was committed to President Donald Trump’s agenda, but failed to address whether he had referred to the president as a “moron,” as NBC reported.

The State Department later denied he had even used the word, an issue Tillerson earlier declined to specifically address.

“The Secretary …. does not use that language to speak about anyone. He did not say that,” State Department spokeswoman Heather Nauert said at a briefing.

The top US diplomat, whose tenure has been dogged with rumours about unhappiness with Trump’s policies and rhetoric, said he was as committed to Trump’s agenda today as he was when he accepted the offer to serve as secretary of state.

The episode is the latest controversy to embroil Trump’s administration which has witnessed a string of high-profile departures and firings in recent months, including his chief of staff, national security advisor and the former FBI director.

NBC reported that in a session with Trump’s national security team and Cabinet officials at the Pentagon, Tillerson had openly criticised the president and referred to him as a “moron,” citing three officials familiar with the incident.

Tillerson sidestepped the issue when taking questions after making a statement at a hastily organised news conference.

“I’m not going to deal with petty stuff like that,” he said, adding, “I’m not from this place (Washington), but the places I come from we don’t deal with that kind of petty nonsense.”