NYSE Euronext would have the option to increase its stake in LCH.Clearnet to 40 percent from 9 percent now, and it would get control of the Paris-based Clearnet SA through which it would clear European share trading, said the source, who was not able to speak on the record.
Markit, a privately held data provider owned by banks and others, partnered with the New York Stock Exchange parent to bid for London-based LCH.Clearnet in the last few weeks.
LCH.Clearnet confirmed it has received offers from exchanges about a tie-up, but that talks are at an early stage. A spokeswoman had no further comment.
Last week, a separate source said Nasdaq OMX Group
Earlier on Wednesday, NYSE Euronext Chief Executive Duncan Niederauer confirmed last week's press reports of the bid, telling analysts at a Deutsche Boerse investor day that Markit is leading the effort.
NYSE Euronext, meanwhile, is planning a $10 billion merger with Germany's Deutsche Boerse AG
Markit declined to comment on Wednesday. A NYSE Euronext spokesman had no immediate comment.
(Reporting by Jonathan Spicer. Editing by Robert MacMillan)