The State Department declared that US Ambassador Robert Godec "has our full confidence and support".
The affirmation by Amanda Jacobsen, spokeswoman for the department's Bureau of Africa Affairs, came in response to a Nation query regarding the call by some Nasa MPs for Ambassador Godec's removal.
Ugunja MP Opiyo Wandayi said on Monday that the opposition grouping planned to lodge a formal protest with the US Senate over Ambassador Godec's "profound vendetta" against Nasa leader Raila Odinga.
Mr Wandayi charged that "Mr Godec's continued stay in the country is injurious to the long-term relationship between the people of Kenya and the US."
The Nasa legislator accused the ambassador of responding to the interests of "only a section of Kenya."