BRUSSELS, July 12 (Reuters) - U.S. grains merchant Bunge and Glencore-backed Viterra have offered to sell assets in two European Union countries in a bid to secure EU antitrust clearance for their $34 billion merger, people with direct knowledge of the matter said on Friday.

The companies put in their offer to the European Commission on Thursday, according to an update on the EU executive's website which did not provide details.

Bunge and Viterra had initially hoped to secure unconditional EU approval after the regulators' preliminary review of the deal but the EU competition enforcer subsequently had concerns on specific European issues, the people said. (Reporting by Foo Yun Chee, Editing by Louise Heavens)