The alliance was executed by the chains’ joint venture Walgreens Boots Alliance Development.
Through this agreement, Walgreens and Alliance Boots are granted with provisions to buy 23% stake in AmerisourceBergen.
Walgreens and Alliance Boots companies can acquire the initial 7% stake in the open market, with options to buy additional 16% in two tranches of 8% each.
The first tranche is to be exercised within a six-month period beginning in March 2016, while the second tranche will be exercisable for a six-month period beginning in March 2017.
The partnership is expected to enable the companies to benefit from greater scale and global opportunities while improving service levels and efficiencies as well as reducing costs.
Commenting on the developments Walgreens president and CEO Gregory Wasson stated that the 10-year agreement with AmerisourceBergen marks a transformational step in its pharmaceutical supply chain.
"We believe this relationship will create a wide range of opportunities and innovations in the rapidly changing U.S. and global health care environment that we expect will benefit all of our stakeholders," added Wasson.
The agreement comes on the back of Walgreens posting Q2 adjusted profits of $915m for the 2013 fiscal.
In addition, the agreement also covers the generic pharmaceutical products that Walgreens self-distributes starting 2014 besides providing it with significant operational benefits.
AmerisourceBergen president and CEO Steven Collis noted, "This new relationship will significantly strengthen and grow our core business and increase our ability to deliver innovative solutions to our customers, and long-term benefits to all of our stakeholders."
Earlier in June 2012 Walgreens had acquired a 45% stake in Alliance Boots with an outstanding option to takeover remaining 55% ownership within two years.