Lufthansa is offering to pay EUR 200 million(US$239 million) to buy its insolvent smaller rival Air Berlin and is prepared to pay up to EUR 100 million to meet operating costs to keep the airline going in the interim, newspaper Bild am Sonntag (BamS) said on Sunday.

Citing sources close to the proceedings, the paper said that there could be three months between signing a purchasing contract and implementing the transaction because the German and European competition authorities would first need to vet any deal, BamS said.

On filing for insolvency last month the Berlin government promptly granted Air Berlin a 150 million-euro bridging loan to keep the airline flying for three months.

On Thursday Air Berlin's creditor committee said it would talk to Lufthansa and Britain's easyJet as possible buyers for the carrier's aviation business, giving three weeks for negotiations.

Sources familiar with the matter said last week Lufthansa was bidding a three-digit millions sum with the offer covering Air Berlin, its leisure airline Niki and regional subsidiary Luftfahrt Gesellschaft Walter.

Lufthansa itself has only said it has made an offer for parts of Air Berlin.

BamS also said its sources had said next week Air Berlin would have to return planes used on its long haul routes to two companies it leases aircraft from.