BRUSSELS (Reuters) - The European Commission has pushed back its deadline for a decision on ChemChina's plan to acquire Swiss pesticides and seeds group Syngenta <SYNN.S> by 10 working days to March 29.

The Commission, which handles competition cases for the European Union, said on Thursday it had extended the deadline at the request of the parties.

EU antitrust regulators opened an in-depth investigation into state-owned ChemChina's $43 billion bid in October, saying the companies had not allayed concerns over the deal.

(Reporting By Philip Blenkinsop; editing by Robert-Jan Bartunek)