Washington, Mar 18 (IANS): Ukrainian prosecutors want to question US President Donald Trump's former campaign chief in connection with a corruption probe and have made repeated requests for assistance from American authorities, a media report said on Saturday.

Prosecutors in Kiev said they have made seven separate appeals over the past two years for help in questioning Paul Manafort, including letters to Federal Bureau of Investigation (FBI) Director James Comey and US Justice Department officials, CNN said in the report.

Ukrainian officials said the US has not responded to those requests.

Under a "mutual legal assistance" treaty, the two countries have agreed to regularly assist each other in law enforcement efforts, such as gathering statements and other evidence for prosecutions.

US authorities confirmed to CNN that the requests were received but declined further comment.

Manafort served as Trump's campaign chief until being pushed out in August 2016.

The official requests from a special prosecution unit in Kiev started in December 2014, and involve a corruption case targeting Ukraine's former Justice Minister Oleksandr Lavrynovych.

Manafort has not been charged with a crime. Prosecutors want him to testify, Ukraine's prosecutor for special investigations Serhiy Gorbatyuk said.

In December 2015, Gorbatyuk's office sent another letter to the Department of Justice asking to question Manafort.

The final letter was dated September 2016: Ukraine's Prosecutor General, the equivalent of a US Attorney General, sent a letter directly to FBI director Comey asking for clarification for why the US authorities would not help.

According to the CNN report, Manafort currently faces an FBI investigation over millions of dollars' worth of payments he allegedly received while serving as advisor for deposed Ukrainian President Viktor Yanukovych.

Manafort has denied those claims.