Merck & Co Inc is ready to acquire large biotech companies with established sales to boost its business and swell the pipeline of experimental medicines, Richard Clark , its chief executive said at the World Economic Forum in Davos.

"As part of our strategy going forward we are aggressively looking at alliances and join ventures and acquisitions of biotech companies," he said.

Clark said Merck had made a strategic decision two years ago to be more proactive in partnering with biotech companies than in the past. He declined to say how large an acquisition might be feasible but said the group had substantial financial muscle.

"I won't give you a market cap number but we have $15 billion in cash and $5 billion of free cashflow every year. We have an outstanding debt ratio," he said.

"Merck has always been very financially conservative in the past, so we can not only fund the dividend and fund the running of the company but me can fund an acquisition," Clark said.

Merck has been over-taken in recent years by New York-based rival Pfizer Inc (PFE.N: Quote, Profile, Research), which is more than twice its size in terms of sales.