(Corrects headline and first and second paragraphs to show EU extends deadline for decision, not Cemex offering concessions)
BRUSSELS, July 29 (Reuters) - European Union antitrust regulators will decide by mid-September whether to clear Mexican cement producer Cemex's proposed acquisition of Holcim's Spanish units, the European Commission said on Tuesday.
The EU watchdog published the Sept. 12 deadline on its website without providing details in line with its policy. Its previous deadline was Sept. 5.
A source told Reuters earlier this month that the Commission had objected to the deal after a preliminary review showed that it would significantly reduce competition in the grey cement market in certain parts of Spain.
Companies typically offer to sell overlapping units to ease regulatory concerns.
Cemex had offered concessions during the Commission's initial scrutiny but these were not considered sufficient. Earlier this month, it won unconditional EU approval to sell its German business to Swiss-based Holcim. (Reporting by Foo Yun Chee; Editing by Martin Santa and David Holmes)