DEERFIELD, Ill. — Walgreen Co. and Alliance Boots have been cleared by regulators to buy an equity stake in AmerisourceBergen Co. as part of their long-term partnership with the pharmaceutical distributor.

The companies said Friday that the regulatory clearances give joint venture partners Walgreens and Alliance Boots the green light to exercise their right to purchase up to 7% of the fully diluted equity of AmerisourceBergen in the open market.

In addition, Walgreens and Alliance Boots have been cleared to exercise equity warrants for 16% in the aggregate of the fully diluted equity of AmerisourceBergen. The warrants will be offered in two tranches exercisable for six-month periods — one starting in March 2016 and the other in March 2017 — and be allocated equally among Walgreens and Alliance Boots.

Walgreens and Alliance Boots have agreed to customary transfer restrictions on their equity stake and to not acquire additional equity of AmerisourceBergen under the terms of a standstill agreement

Plans call for a Walgreens executive to be appointed to AmerisourceBergen’s board upon Walgreens and Alliance Boots together acquiring a 5% equity interest. An Alliance Boots executive will be appointed upon exercise in full of the first warrants.

According to Walgreens, the regulatory clearances allow up to a 25% investment in AmerisourceBergen, including the effect of any stock buybacks by AmerisourceBergen.

The three companies announced their landmark partnership on March 19. Along with enabling Walgreens and Alliance Boots to acquire an equity interest in AmerisourceBergen, the three-part deal broadens the current relationship between AmerisourceBergen and Walgreens beyond specialty pharmaceuticals to a 10-year primary distribution agreement for branded and generic drugs. The agreement also calls for AmerisourceBergen to access generics and related pharmaceuticals through the Walgreens and Alliance Boots joint venture, Walgreens Boots Alliance Development GmbH. The venture was formed at the end of October.

Valley Forge, Pa.-based AmerisourceBergen said Friday that it expects the new agreements to contribute an incremental $25 billion in revenue and about 20 cents in earnings per share in fiscal 2014, excluding the amortization of certain expenses related to the transaction and the warrants issued, certain nonrecurring costs, a potential LIFO charge, and net of certain start-up expenses.