Will probe possible surveillance of Ukraine envoy: Pompeo

US Secretary of State Mike Pompeo promised Friday to investigate whether the ousted ambassador to Ukraine was being spied on by President Donald Trump's supporters but said he was unaware if so.

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House Democrats, who cited Trump's dismissal of ambassador Marie Yovanovitch as they impeached him, released documents this week that suggested that the envoy was under private surveillance.

After days of the State Department not commenting, Pompeo said in two interviews with conservative media that he had not previously heard of any surveillance of Yovanovitch.

"We do our best to make sure that no harm will come to anyone," he told radio host Tony Katz.

"We will do everything we need to do to evaluate whether there was something that took place there," he said.

"I suspect that much of what's been reported will ultimately prove wrong, but our obligation - my obligation as secretary of state - is to make sure that we evaluate, investigate," he said.

Pompeo said he has never met Lev Parnas, a Ukrainian-born American who was working with Trump's personal lawyer, former New York mayor Rudy Giuliani.

The documents released by House Democrats detailed exchanges in which Yovanovitch's location was discussed, indicating that she may be under watch.

Ukraine earlier announced a probe amid indications that officials joined the alleged surveillance effort.

Trump last year removed Yovanovitch as ambassador and later denounced her in a call with his Ukrainian counterpart Volodymyr Zelensky that triggered his impeachment.

Witnesses testified that Trump saw the veteran diplomat as an impediment in his bid to pressure Ukraine to investigate his domestic rival Joe Biden, whose son served on the board of a Ukrainian company.

Pompeo, a stalwart ally of Trump, has come under sharp criticism from former career diplomats for not robustly defending Yovanovitch either to the White House or in public.