MOSCOW – Russian tycoon Mikhail Prokhorov's Onexim group may increase its stake in UC Rusal, the world's biggest aluminium producer, to 19,16% from the previously expected 18,5%, a Russian newspaper said on Thursday.

Vedomosti business daily quoted unindentified sources close to Onexim and Rusal as saying Prokhorov had agreed to convert $1,8-billion of the $2,8-billion owed to him by Rusal into the indebted company's stock.

UC Rusal and Onexim both declined to comment.

The sources did not say what would happen to the rest of the debt. The previous agreement on Rusal's debt to Onexim was reached in March.

If the report proved to be true the share of Rusal's main owner, Oleg Deripaska, would reduce to 53,39% from 53,8%.

The stakes of Renova Group, controlled by businessmen Viktor Vekselberg and Len Blavatnik, would fall to 17,76%  from 18% and that of Swiss-based commodities trader Glencore to 9,68% from 9,7%, Vedomosti said.

Senior bankers told Reuters last month that Rusal had to reach agreement with foreign creditors on $7,3-billion of debt by mid-November if the company's planned IPO is to proceed.

The debt standstill agreement, due to expire on Oct. 30, was extended until mid-December in order for all the banks to reach agreement on Russia's largest ever restructuring.