"The president is the CEO of the country," Haley told ABC News Chief Anchor George Stephanopoulos on "This Week" Sunday. "He can hire and fire anyone he wants."
Stephanopoulos asked Haley if she found herself having to explain to foreign diplomats Trump's domestic policy decisions, including his surprise choice to fire the FBI director, noting that a fellow U.S. ambassador, Dana Shell Smith in Qatar, tweeted last week that her job was becoming "increasingly difficult."
Haley demurred at that suggestion, saying that no one in her job at the U.N. had asked her about Trump's move.
She added that she believes the criticism of Trump stems from discomfort with his propensity to act on his decisions.
"I think what you can see is that this is a president of action," she said of Trump. "The reason people are uncomfortable is because he acts."
Stephanopoulos asked the ambassador if the president sought a pledge of loyalty from her, referring to reports this week that the president had asked this of Comey at a January dinner.
Haley said no, but added that in her former position as governor of South Carolina demonstrations of "loyalty and trust" were important to her.
Regarding the president's tweet this week warning the fired FBI director that he better hope there are no "tapes" of their private conversations, Haley seemed unconcerned by the possibility that the president is taping conversations.
"I assume I'm being taped everywhere," she said.
Haley also addressed a range of other topics, including North Korea's latest missile launch Saturday night.
She said there is a growing international consensus to impose further sanctions on North Korea over its nuclear program and that the U.S. will "tighten the screws" on North Korean President Kim Jong Un's government.
Trump has said in the past that he would be willing to sit down with Kim Jong Un, but Haley said such a meeting would only happen if North Korea meets certain conditions.
"A missile test is not the way to sit down with the president," Haley said.