PARIS - French utility group Veolia said on Monday it would improve its offer to buy the bulk of Engie's stake in smaller rival Suez by Sept. 30.

Veolia last month offered 2.9 billion euros ($3.37 billion) for a 29.9% stake in Suez owned by Engie, with a view to subsequently taking full control of Suez by buying up more shares.

Engie, which owns almost 32% of Suez, rejected Veolia's initial advance but has said it would consider a higher offer.

Veolia's CEO Antoine Frerot said on Friday that the company would increase its offer to buy a 29.9% stake in Suez and had the capacity to do so. 

($1 = 0.8596 euros)

(Reporting by Matthieu Protard; Editing by Kim Coghill) ((matthieu.protard@thomsonreuters.com; +33-1-49495381;))