(Reuters) - Sanofi (>> Sanofi) is considering a bid for Swiss biotech company Actelion (>> Actelion Ltd), rivaling an offer made by U.S. healthcare company Johnson & Johnson (>> Johnson & Johnson), Bloomberg reported.

French drugmaker Sanofi is working with advisers to assess its options, people familiar with the matter told Bloomberg. (http://bloom.bg/2h8qooh)

Sanofi has made its interest known to Actelion but has not decided if it will proceed with a bid, Bloomberg said, citing the sources.

To gauge potential interest for Actelion, advisers have also reached out to other drugmakers including Switzerland's Roche Holding AG (>> Roche Holding Ltd.) and Pfizer Inc (>> Pfizer Inc.), the Bloomberg report said.

J&J said last month it was in preliminary talks with Actelion about a takeover of Europe's largest biotech firm, which was then valued at about $20 billion.

Lung disease specialist Actelion, which confirmed the J&J move then, had warned that there was no certainty of a deal.

Sanofi, J&J, Actelion, Roche and Pfizer were not immediately available for comments.

(Reporting by Akankshita Mukhopadhyay in Bengaluru; Editing by Maju Samuel)