Blues are said to be in talks with the 27-year-old American international centre-back, who is now a free agent, and are believed to be close to signing Onyewu on a three-year contract.
"Oguchi Onyewu is on his way to the Premier League with newly-promoted Birmingham," the statement on the official Liege website read.
"More and more, it appears that England and more precisely Birmingham will be his new home in Europe.
"The manager Alex McLeish, according to details on the other side of the channel, has made him a priority considering his status as a free agent.
"The two parties are close to a final agreement and a three-year-old contract could be signed this weekend."