Drug store chain Walgreens plans on buying a 45 percent stake in Alliance Boots, a European pharmacy retailer. The stake is expected to cost the company $6.7 billion.

There is great potential for Walgreens to eventually take over Alliance Boots by 2015. The deal will allow the drug store chain to expand its markets internationally, and allow Alliance Boots the opportunity to be a well-known pharmacy retailer in the United States.

This is by far one of the biggest negotiations between a drug store and pharmacy retailer, consisting of over 11,000 stores and covering a span of 12 countries.

"Today's announcement represents an exciting opportunity to accelerate our five core strategies and advance that mission in the U.S. and now internationally," Gregory Wasson, chief executive of Walgreens, said in a statement to The New York Times. 

This is executive chairman of Alliance Boots, Stefano Pessina's, largest deal since buying the European company for close to $22 billion.

"This strategic transaction represents a further vital step in achieving our vision of becoming a global healthcare leader," Mr. Pessina said.

Walgreens offered to pay Alliance Boots $4 billion cash, in addition to $2.7 billion in company stock to buy the pharmacy retailer. Walgreens can also purchase the rest of the stake in Alliance Boots in three years, for a total of $9.5 billion cash and stock. The exact price has not yet been settled upon, as it depends on how Walgreens' shares are doing and changes in the foreign exchange.

The deal between the two companies is said close by September 1. Walgreens expects to have $1 billion in savings by the end of 2016.