Legal red tape in Ukraine and a lack of help from the United States have left Ukraine’s investigations of former Donald Trump campaign chief Paul Manafort in legal limbo, senior prosecutor Serhii Horbatiuk told Reuters on Friday.

The cases relate to alleged misuse of Ukrainian state funds under former president Viktor Yanukovich, whose Party of Regions Manafort advised.

Last November, Horbatiuk, who heads special investigations at the general prosecutor’s office, warned that corruption probes, including those linked to Manafort, were at risk of being buried due to their transfer to a sister agency.

Since then, most have been returned to his team’s jurisdiction, apart from the three cases in which Manafort figures. Horbatiuk said these were in effect frozen as the general prosecutor’s office had not decided which agency should handle them.

 As a result, “investigators and prosecutors have not been able to carry out investigative action”, he said by messaging service.

General Prosecutor Yuriy Lutsenko said this month that Ukraine could not progress with the cases until U.S. investigations into Manafort produced results.

Horbatiuk said Ukraine had sent repeated requests to Washington for help, most recently in March.

“The Justice Department’s longstanding failure to carry out the requests for international legal assistance, sent in December 2014 and March 2015 in one of the criminal cases, is of course holding up the investigation,” he said.

Manafort has gained global attention as a figure in U.S. Special Counsel Robert Mueller’s investigation into alleged Russian meddling in the 2016 U.S. election.

In the United States, Manafort faces two indictments accusing him of conspiracy against the United States, conspiracy to launder money, failing to register as a foreign agent for lobbying work he did for the pro-Russia government of Ukraine, bank fraud and other offences.

 He has pleaded ‘not guilty’ to the charges, none of which make reference to alleged Russian interference in the election, or to accusations of collusion between Moscow and Trump’s campaign.

Writing by Alessandra Prentice; Editing by Kevin Liffey