Heineken is launching a search for a second agency to handle global media planning and buying at the world's third-largest brewer.

The Netherlands-based company has been working with Starcom Mediavest Group since 2012, when it consolidated work handled by 14 worldwide agency partners into one relationship with the Publicis Groupe media network.

AAR Partners, London, is handling the current search process which is being led by Gregory Kukolj, Heineken's global head of media and digital. He did not disclose the marketer's global spending on the company's portfolio of brands, which include Amstel, Tecate and Dos Equis.

When SMG won the business in 2012, prevailing over WPP's Mindshare, global spending was estimated at $335 million. In the U.S. alone last year, Heineken spent $153.2 million on measured media according to Kantar Media.

Kukolj, who joined Heineken right before SMG was selected four years ago, said he is looking for an agency with complementary skills and geographic reach to SMG. He said the post-consolidation experience has taught Heineken a lot about how to drive consistency in and storytelling and in pushing for greater media efficiencies at the company.

Kukolj said Heineken will continue to work with SMG in the 30 markets where it has an existing relationship with the agency. He denied any intent to bring in an agency to replace SMG, which handles Heineken's top 15 markets, which account for 80 percent of the company's top 30 media market budgets.

"We are not adding an element of competition.This is about future proofing our media partnership," he told Adweek. "This is a natural evolution after going from fragmentation to one agency. We are not creating fears within a network where we work well with a partner in 30 markets."

Those fears are understandable, as SMG has had a tough time recently, with the agency hit by a loss of business from major clients like Procter & Gamble, Coca-Cola, Walmart and Mondelez.

The media review comes just a year after Heineken unexpectedly shifted creative duties on its flagship brand to Publicis Worldwide—SMG's Publicis Groupe corporate sibling—from Wieden + Kennedy. That move stunned the industry, as it occurred right before Heineken received 2015 Marketer of the Year creative recognition at the Cannes Lions, earned in part because of the W+K work.