Trump administration reports of severe health problems resulting from "attacks" on U.S. diplomats in Cuba are "deliberate lies" and a pretext to roll back progress made toward normalizing relations between the two countries, Cuban Foreign Minister Bruno Rodríguez said Thursday.

"It is high time for the United States to tell the truth or otherwise present evidence," Rodríguez said at a news conference in Washington. "The Cuban government has no responsibility whatsoever for these incidents," he said.

His comments marked a sharp change in Cuba's approach to the charges. Immediately after a September meeting in Washington with Secretary of State Rex Tillerson, Rodríguez pledged Cuba's ongoing cooperation in finding the cause of the mysterious diplomatic ailments and expressed hope that the issue would not undermine relations.

Within the week after that visit, however, the Trump administration announced it was dramatically reducing the size of the U.S. Embassy in Havana, suspending issuance of U.S. visas to Cubans there, advising Americans not to travel to the island and expelling 15 Cuban diplomats from Havana's embassy in Washington.

The Cuban government has repeatedly denied any responsibility for diplomatic health problems. It has facilitated four visits by FBI investigation teams to the island and said its own investigations have turned up no apparent cause.

The State Department has said that 24 diplomats assigned to the embassy have suffered "attacks" that began late last year and continued until late summer.

It has described symptoms, sometimes verified months after the attacks, include hearing loss, balance problems and traumatic brain injury. In some cases, personnel were said to have fallen ill after hearing unusual noises, either in their residences or in hotels, leading to speculation they had come under some sort of sonic assault.

While saying that victims were "receiving comprehensive medical evaluations and care," the State Department has not released the names of the afflicted, any specific information about their health or results of investigations thus far.

Even before reports of the attacks were made public, President Trump announced what he said was a new policy toward Cuba that would roll back many of the moves toward normalization undertaken during the Obama administration. After more than a half-century of estrangement, diplomatic relations between Havana and Washington were resumed in July 2015.

Although the congressionally mandated economic embargo against Cuba continued, President Barack Obama issued regulatory changes that allowed increased commercial ties and expanded travel to Cuba by U.S. citizens.

During his campaign, Trump said he would "terminate" the Obama normalization if Cuba would not cut a "better deal" with the United States.

Rodríguez's remarks echoed a speech he made at the United Nations this week, where the General Assembly voted for the 26th time to condemn the ongoing U.S. embargo. The United States has been alone — except for Israel and an occasional Pacific island nation — in voting against the measure each time.

The steps the Trump administration has taken against Cuba, Rodríguez said at the Thursday news conference, "have been accompanied by repeated disrespectful and offensive statements toward Cuba by the U.S. president, thus relaunching the hostile rhetoric of the periods of sharpest confrontation" between the two countries.

While Cuba has offered full cooperation and conducted its own investigation, he said, Cuban experts have been given no access to "affected persons" or the diplomatic localities where the alleged attacks took place. Cuba, he said, has not been given "one single source or fact" relating to the incidents, including timelines or even elementary medical information.

Cuba's preliminary conclusion, he said, is "that there is no evidence whatsoever of the occurrence of the alleged incidents or the cause . . . of these ailments. . . . Neither is there any evidence suggesting that these health problems have been caused by an attack of any sort during their stay in Cuba." Rodríguez said he met with congressional and business officials during his one-day stop in Washington but with no one in the administration.

"If Havana were really an unsafe place," Rodríguez said, "the U.S. authorities would not have requested 212 visas for relatives and friends of diplomats between January and October, nor would [diplomats assigned to Cuba] have made more than 250 pleasure trips outside Havana."