German lender Commerzbank will shed more than 5,000 jobs, 10 percent of its workforce, under a preliminary deal with staff representatives to cut costs, a person close to the company told Reuters on Tuesday.

While two people familiar with the negotiations said the two sides have in principle agreed the extent of the cutbacks, a labor source dismissed the number of more than 5,000 jobs as "clearly too high."

Commerzbank declined to comment while a spokeswoman for trade union Verdi described the number of jobs affected as "inexplicable."

The lender is retrenching as part of a 2 billion euro ($2.7 billion) overhaul announced in November, which includes a revamp of its retail business in Germany. Labor representatives have sought to avoid compulsory redundancies.

Flagging the cuts, Chief Financial Officer Stephan Engels said in May that 2013 would be a year of transition for the bank, which posted a net loss of 94 million euros in the first three months as it booked a 493 million euro restructuring charge linked to 4,000-6,000 job losses.

Daily Handelsblatt reported that as part of the agreement, none of Commerzbank's 1,200 branches would be closed.

Commerzbank has said it wants to shed 1,800 positions at its retail banking unit by the end of 2015 but internal documents sent to staff have shown that more jobs would go if certain targets are not met.

The bank, 17 percent state-owned since a bailout during the financial crisis, currently employs 53,000 staff at group level.

A person familiar with the matter has told Reuters the bank would introduce longer business hours at branches, requiring staff to work changing shifts and be flexible about relocating.