WASHINGTON — Secretary of State Mike Pompeo said Friday he “never heard” that his top envoy to Ukraine, Ambassador Marie L. Yovanovitch, might have been under surveillance before she was recalled to Washington, accused of being disloyal to President Trump.

“Until this story broke, I had, to the best of my recollection, had never heard of this at all,” Mr. Pompeo told Hugh Hewitt, a popular conservative radio show host.

He did not offer any other details during the 11-minute interview except to say that he had “never met” Lev Parnas, an associate of Rudolph W. Giuliani, Mr. Trump’s personal lawyer. In text messages released this week by House Democrats, Mr. Parnas is shown to have been in communication last March with a Trump supporter and Republican congressional candidate, Robert F. Hyde, an ex-landscaper with a history of erratic episodes who claimed to have been in touch with someone in Kyiv who was conducting surveillance on Ms. Yovanovitch.

Ms. Yovanovitch was told to return to Washington in late April, months ahead of schedule, after Mr. Trump’s eldest son described her as a “joker,” and other conservatives denounced her for unfounded accusations of corruption and disloyalty to Mr. Trump.