(Reuters) -- Greece could reach a bond swap deal with private creditors to reduce its debt load by the end of next week, with a formal offer possible by early February, a Finance Ministry source said Thursday.

We may have the formal public offer by the beginning of February, the official added.

Time is running short to reach a deal on a voluntary debt exchange, the Institute of International Finance (IIF) warned earlier on Thursday after crunch talks with Greece's prime minister.

Negotiations between Athens and its creditors, spearheaded by the IIF, have entered the final stretch ahead of a major bond redemption in March. The IIF said key areas remained unresolved.

(Reporting by Dina Kyriakidou)