US-based Watson Pharmaceuticals (NYSE:WPI) has not ruled out a $600 million takeover bid for Australian healthcare group Sigma Pharmaceuticals (ASX:SIP).

Watson chief executive Paul Bisaro said its company actively was seeking acquisition opportunities, both locally and abroad.

''On the branded M&A side, I mean, we're probably looking more,'' Mr Bisaro said.

''As for commenting on any specific international acquisition opportunity, I'm going to decline to do that. Only to say that we continue to look for opportunities that are presented and to the extent it makes sense for Watson to make a move into those markets, we'll be there.''

His remarks came after BusinessDay published last week that the American company is eyeing Sigma's generics business. As Watson supplies drugs to Sigma for distribution, it already has an understanding of its inner workings.

According to Mr Bisaro, Sigma's earnings slumped this year and the unsteady trading conditions in local prescription drugs had hit turnover.

''Sigma had a bit of a hiccup in the first quarter, first two quarters really in Australia, and that did affect our revenues a bit in Australia,'' Mr Bisaro said.

''But we do expect a pick-up in the second half.''

Mr Bisaro said his company is very much interested in healthcare products.

''We're probably looking more for product opportunities and pipeline opportunities and biologic opportunities than we are for growing into another therapeutic category,'' he said.

Acquiring all or part of Sigma would expand Watson's breadth in the region.

Watson announced $US2.8 billion ($A14 billion) revenue in 2009 and a net profit of $US384 million. Its generics business posted a revenue of $US1.7 billion.