* Sanofi "leaning towards" upping bid by $1-2/shr -Bloomberg
* Would prefer friendly talks to hostile bid
* Genzyme has not talked to "white knights", CEO tells FT
* Sanofi stock down 0.1 pct, Genzyme down 0.8 pct in Germany (Adds analyst comment, shares, background)
By Caroline Jacobs and Quentin Webb
PARIS/LONDON, Sept 29 (Reuters) - Sanofi-Aventis is considering whether to raise its $18.5 billion bid for U.S. drugmaker Genzyme as soon as next week, Bloomberg said on Wednesday, citing people with knowledge of the matter.
France's largest drugmaker is "leaning towards" raising the $69-a-share offer by $1 or $2 a share, Bloomberg said. It has not ruled out a hostile bid but would prefer friendly negotiations, the report said.
Sanofi executives and top advisers will meet later this week to discuss how to proceed and a final decision has not been taken, the article cited one of the people as saying.
A Sanofi spokesman declined to comment on the report. He reiterated to Reuters that Sanofi had made one offer at $69 a share, and had not made or discussed any other offer with Genzyme's board, management or shareholders.
If Sanofi decided to match the market price of Genzyme shares, some analysts said management would be under pressure to begin negotiations or give Sanofi access to its books, particularly in the absence of any other bidder.
"If Sanofi raised the offer by $1 to $2, it would match what market is indicating at the moment Sanofi should be paying," Helvea analyst Karl Heinz Koch said.
"That by itself will put pressure on Genzyme management to at least sit around the table and explain why they believe $71 is not enough, and give Sanofi something they can base their pricing on."
NO WHITE KNIGHT
Separately, Genzyme Chief Executive Henri Termeer told the Financial Times he could step down in mid-2011 and Genzyme's board had held no talks with an alternative "white knight" buyer.
Genzyme has rejected Sanofi's cash offer as dramatically undervaluing the company, specialised in rare diseases, saying it did not justify entering merger talks. Still, Termeer told Reuters in August he was willing in principle to sell the company he founded.
Genzyme shares in the United States closed at $71.50 on Tuesday after reaching a year-high at $71.99 on Sept. 27, up from a year-low of $45.39 at the end of May.
Termeer was quoted as saying in the Financial Times he would be ready to retire following confirmation of late-stage trial results for the company's Campath multiple sclerosis drug due in mid-2011.
Sanofi wants to buy Genzyme to fuel growth as some of its key treatments lose patent protection. Buying Genzyme would give it a stronger foothold in the United States, the world's biggest drugs market, and add rare diseases to its portfolio.
Sources previously told Reuters that Genzyme sought an offer of at least $75 per share before Sanofi could review its books, while some investors want $80 a share in a deal.
"I'm not in any way offended (by the Sanofi-Aventis bid). They have to recognise our value rather than be opportunistic," Termeer told the FT. "The company is recovering in a significant way, and pulling in value."
Shares in Sanofi slipped 0.1 percent to 49.78 euros by 0855 GMT, broadly in line with the DJ health index. Frankfurt-traded Genzyme shares fell 0.8 percent to 52.42 euros. (Additional reporting by Karolina Tagaris; Editing by Erica Billingham and Louise Heavens)