By Natalia Drozdiak 

BRUSSELS-- Bayer AG and Monsanto Co. face an in-depth investigation by the European Union into their roughly $57 billion merger over concerns that it could lead to higher prices and fewer options for consumers in markets including pesticides and seeds, throwing into doubt the companies' plan to complete the tie-up by the end of the year.

Bayer Chief Executive Werner Baumann has recently said he expected the in-depth probe by the EU, but nonetheless counted on completing the deal before year-end. Still an advanced investigation by the EU is likely to complicate that timeline.

The EU on Tuesday said it was giving itself until Jan. 8, 2018 to complete the review, and regulators rarely complete their reviews well in advance of their set deadline. That date could also be pushed back if there are any delays or extensions to the review.

In a statement, Bayer said it "looks forward to continuing to work constructively with the commission with a view to obtaining the commission's approval of the transaction by the end of this year."

The EU on Tuesday said it was concerned the Bayer-Monsanto deal would lead to higher prices, lower quality, less choice and less innovation in the markets for pesticides, seeds and for plant traits, which can be developed in laboratories and introduced in some varieties of plants.

Bayer and Monsanto have already submitted commitments to the EU in a bid to win approval, according to the regulator. But those were "insufficient to clearly dismiss [the EU's] serious doubts as to the transaction's compatibility with the EU merger regulation."

The deal is the last in a batch of three major mergers in the agrochemical sector that are set to reshape the industry. The EU has already cleared Dow Chemical Co. and DuPont Co.'s deal as well as China National Chemical Corp.'s roughly $43 billion takeover of Swiss seed and pesticide maker Syngenta AG. In both cases the companies had to make considerable concessions to win clearance.

Still, that leaves Bayer-Monsanto seeking approval in an already consolidated industry, which in turn could require Bayer and Monsanto to offer up more extensive remedies, like selling a wider array of assets than expected, in exchange for regulatory approval.

Write to Natalia Drozdiak at natalia.drozdiak@wsj.com

(END) Dow Jones Newswires

August 22, 2017 09:49 ET (13:49 GMT)