Aventis' staff are worried about the "takeover virus"

The firm said net profits rose 17.5% in 2003 to 2.44bn euros ($3.1bn; �1.7bn), although sales fell 4.5% in the face of the weakening dollar.

Aventis will detail how it plans to ward off the bid later on Thursday.

Sanofi's share-based hostile offer has fallen in value as its share price has slid, but the firm has said it sees no need to put more money on the table.

"Their hostile bid is a cheap attempt to transfer their risks to our shareholders," said Aventis chief executive Igor Landau.

"It is very clear: they need us, we don't need them."

'Champion'

Hostile takeover attempts are rare in continental Europe.

Sanofi-Synthelabo may have been encouraged in its late January offer - worth 47.8bn euros at the time but 46.8bn now - by signs of support from the French government for a "national champion" in the pharmaceutical market.

A combination of the two companies would generate the third biggest firm in the business, behind US giant Pfizer and the UK's Glaxo SmithKline.

Sanofi's pipeline, the drugs it has in development, is thought in some circles to be stronger than its counterpart, justifying a valuation which is about the same as Aventis' despite the latter having twice the sales.

And brokerage ING noted that only a year ago it was Aventis' Igor Landau who was suggesting a merger.

"It seems reasonable to ask why it would no longer make sense," the firm wrote.

Battle

But Aventis sees things differently, and is lining up for a stern defence.

Although sales growth in its top allergy drug Allegra slowed in 2003, it said newer products were performing strongly.