Rex Tillerson. Spencer Platt/Getty Images Secretary of State Rex Tillerson is at odds with the US ambassador to the United Nations Nikki Haley, adding to the drama of what has already been a tumultuous week for the top US diplomat, according to a New Yorker report on Friday.

"Rex hates her," a senior US official said about Tillerson's feelings toward Haley. "He f------ hates her."

The official made that comment after suggesting Haley proved to be "the most effective diplomat" in the simmering rift between the US and North Korea over that country's missile program.

"Nikki's getting it done," the US official said. "She's bringing home the bacon."

Officials have privately complained that Haley was overstepping elements of Tillerson's agenda and was not notifying the State Department prior to making public statements on subjects under the department's purview, CBS News reported this week.

On North Korea, Haley has long been a proponent of increased UN sanctions against the regime, often echoing President Donald Trump's bellicose rhetoric, while Tillerson has expressed caution and asked for negotiations with China in hopes of influencing North Korea.

Haley also reportedly invited herself to an Iran nuclear deal meeting that included several other participating nations last month. She sat behind Tillerson, which some foreign diplomats who were present reportedly interpreted as a signal of distrust toward the secretary of state, CBS News reported. Haley's staff members denied the assertions.