The high-risk saga of European telecom consolidation took another twist on Wednesday as one powerful predator tightened its grip on its prey while another acquisition target moved firmly into play.

Telef�nica SA’s chances of success in its 17.7 billion pounds ($31.2 billion) offer for U.K. mobile operator O2 plc received a huge boost after its most likely challenger, Deutsche Telekom AG, declared it would not bid.