German Chancellor Angela Merkel said Wednesday she remained convinced that the EU-China investment deal was an "important undertaking" even as strained relations complicate the agreement's ratification, AFP reported on Wednesday.

"Despite all the difficulties that will surely arise with the ratification, it is a very important undertaking," Merkel said in a speech to her conservative CDU/CSU alliance.

The massive investment pact laid the foundations for "mutually beneficial" trade, she said, citing more reciprocity on market access, compliance with international labor standards and the brand protection of regional products as some of the deal's advantages.

The European Union and China in late December approved a major investment pact, wrapping up seven years of painstaking negotiations.