WASHINGTON (AP) — When Kurt Groszhans set out from North Dakota for Ukraine in 2017, he was eager to connect with his family's ancestral homeland and to farm the rich, black soil for which the country is known.

But his farming venture with a law professor who's now a high-ranking Ukrainian government official soon collapsed in acrimony and accusations, culminating in his arrest last November on charges of plotting to assassinate his former business partner. His family and supporters say the accusations are bogus and designed to silence Groszhan's claims of corruption in Ukraine, a country pulled between Russian and Western interests and straining to shed its reputation for graft and cronyism.

The case is unfolding as Ukraine braces for a potential Russian invasion and as the U.S. has ordered the families of American personnel at the U.S. Embassy there to evacuate,. The upheaval has Groszhan's family afraid that the North Dakota farmer could be left behind, with the U.S. government preoccupied with broader concerns of possible military action and geopolitical chaos.

“We're terrified for my brother's well-being right now, especially everything that you're hearing in the news with the Russian troops on the border,” his sister, Kristi Magnusson, said in an interview with The Associated Press. With fears an invasion could force the evacuation of U.S. diplomatic staff, she called on the Biden administration and the State Department to "use their leverage” to get him home.

“If the embassy is not there to check on him and make sure that he's doing OK, we don't know what will happen,” she added.

Asked for comment, the State Department said the administration took seriously its responsibility to help detained Americans and was closely following the case, but declined to comment further.

Republican Sen. Kevin Cramer of North Dakota, who recently visited Groszhans at the detention center where he awaits trial, said the episode has “created friction between at least me and them, if not our two governments, that should be alleviated" at a time when U.S. and Ukrainian interests should be aligned in countering the threat from Moscow.

“This bit of friction is unnecessary," he added. “And I think we could relieve all of us of it simply by releasing Kurt.”

Groszhans, a 50-year-old farmer from Ashley, North Dakota, traveled in 2017 to Ukraine, where his ancestors are from. The chance to work the country's coveted black earth was a “dream come true,” and he invested a large sum to get a farming operation up and running, his sister said. In a country with a prized agricultural sector, Groszhans was proud of his work, she said, sending pictures to his family of his crops.

Once there, he connected with a law professor, Roman Leshchenko, who offered himself up as a native speaker with knowledge of the local farming business and regulatory requirements. Grozhans named him the director of his company.

Things fell apart quickly.

Groszhans has alleged in a lawsuit and in an internet post that Leshchenko began embezzling money from him, defrauding him of over $250,000 in total and transferring funds to a family company. Groszhans has been vocal about his allegations, describing himself in a Medium post in August as a “humble” but deceived investor.

“Probably, I am not the first or the last American investor who made a mistake in the person hired as a manager. But the personality of this manager makes my case unique,” he wrote.

Leshchenko declined to comment to the AP, but has denied the embezzlement claims in interviews with the Ukrainian media and has insisted that the men had agreed that Leshchenko's company would run the farming business.

He's leveled his own accusations against Groszhans, alleging that the American farmer planted genetically modified soybean that is banned from cultivation and sales in Ukraine and it was that discovery that prompted Leshchenko to resign from the company and was the source of their dispute.

“The circumstances of this criminal proceedings must be verified as part of the pre-trial investigation conducted by the National Police and only on the basis of the results of which, after the relevant facts and their evidence have been clarified and established, the prosecutor’s office can make appropriate procedural decisions,” Tetyana Kozachenko, a lawyer for Leshchenko, told The Associated Press.

Ukrainian media that began looking into the conflict reported that Leshchenko had used some of the funds for a roughly $60,000 contribution to the 2019 campaign of current Ukrainian President Volodymyr Zelenskyy, who later named Leshchenko the government's minister of agrarian policy and food.

The AP was unable to independently confirm the contribution. Zelenskyy’s office did not respond to a request for comment.

Amid controversy about the contribution, Leshchenko was interviewed by the Kyiv Post last year. The article said the $60,000 donation came from Leshchenko’s dying father. Leshchenko said he and his father saw Zelenskyy “as the only person who wants to change Ukraine, bring structural reforms."

Magnusson says Leshchenko ultimately did return some money to her brother, but also threatened to have him arrested if he didn't stop talking publicly about his fraud accusations.

In November, Groszhans was arrested along with his assistant on charges of plotting to assassinate Leshchenko, allegations that Groszhans' supporters say are wholly fabricated but may have arisen from Groszhans' hiring of a private investigator to dig into Leshchenko as part of his litigation.

The arrest, his family and supporters believe, was a pretext for silencing his allegations, particularly in a country that has sought to shore up diplomatic and military support from the U.S. through reassurances it is making a serious effort to curb corruption.

“My brother has never in all of his 50 years of life ... been in trouble with the law,” Magnusson said. “And we don’t believe any of this can be true because why would you want to assassinate somebody if you’re trying to collect money back that is legally owed to you?”

His supporters are asking the Biden administration to formally designate him a wrongful detainee, a classification that would allow for his case to be reassigned to the Office of the Special Presidential Envoy for Hostage Affairs at the State Department.

But his family fears the window for attention to Groszhan's case may be limited, given the potential for an incursion by Russia and the dwindling diplomatic presence by the U.S.

“It just makes us more and more concerned for him and for his safety to know that these people could be leaving and Kurt is forgotten about, and he's left behind," Magnusson said.