Secretary of State Mike Pompeo on Wednesday defended his response over mysterious brain injuries suffered by a number of US diplomats, saying an investigation was underway and that anyone responsible would be held accountable.
Starting in late 2016, US diplomats in Havana began to report ear pain and other symptoms from a high-frequency noise, leading President Donald Trump's administration to withdraw half the US embassy staff and to expel Cuban diplomats in retaliation.
Similar cases began emerging in 2018 among US personnel in the southern Chinese city of Guangzhou, with Pompeo initially linking the situation to the episodes in Havana.
But The New York Times, in an investigation published Tuesday, said that the State Department had played down the incidents in China and did not open a similar investigation.
The newspaper said that a clandestine CIA officer in Moscow also suffered debilitating headaches that forced him into retirement, raising suspicions that Russia was waging non-traditional warfare in multiple sites.
"It's a very complicated situation and there is not yet any complete US government analysis which definitively tells us precisely how these all came to be, whether they're part of a single cohort," Pompeo told reporters.
"There are multiple theories, and you should know there are significant US government resources... three-plus years on, devoted to getting to the bottom of this and then holding those responsible accountable should we determine that that's required," he said.
He hit back at suggestions that there was a politically motivated gap in responses, with Trump eager to find a pretext to end former president Barack Obama's reconciliation with Cuba but not to confront Russia or China.
"There were no politics attached to this. The suggestion somehow is that we didn't protect our officers because of some larger political objective -- that is patently false," Pompeo said.
Pompeo, who led the CIA before Trump named him the top US diplomat, said he was personally committed to making sure all diplomats are "safe and healthy and protected."
Cuba has denied any involvement in the mysterious attacks, with even some critics of the communist state questioning why it would invest in high-tech warfare against US diplomats after supporting the re-establishment of diplomatic relations.
One scientific study last year concluded that the diplomats in Cuba suffered not a sonic attack but from the sound of a local variety of crickets, although the finding drew wide skepticism.