Germany on Tuesday formally rejected UniCredit's offer for Commerzbank shares, citing a low price and concerns about what it called the Italian lender's aggressive approach.

UniCredit's initial offer period for Commerzbank shares is winding down, with both banks digging ​in their heels in the months-long battle for control of one of Germany's most important lenders.

On Monday, the Italian bank hailed the fact that it had exceeded the 30% threshold it had set for this takeover bid. The Milan-based lender launched its bid, valued at 35 billion euros ($40.6 billion), in early May to gain control of its German rival and cement its status as a European heavyweight.

The ​German government holds a 12% stake in Commerzbank acquired in the wake of the ⁠2008 global financial crisis and has long objected to UniCredit's campaign for a tie-up.

"Accepting the offer was ​already not an option from a financial point of view, as it does not include an appropriate premium ​on the current share price of Commerzbank’s shares," the country's finance agency said on Tuesday.