UPDATE 1-Siemens set to win EU approval for $4.5 bln Mentor deal - sources

BRUSSELS/FRANKFURT, Feb 23 (Reuters) - German engineering group Siemens is set to gain unconditional EU antitrust approval for its $4.5 billion bid for U.S. software company Mentor Graphics, its biggest deal in this area in a decade, two people familiar with the matter said on Thursday.