FRANKFURT (Reuters) -Commerzbank on Wednesday defined UniCredit's approach for a potential tie-up as "hostile", and said there had been no discussion of it with the Italian bank in the past two years, despite UniCredit CEO Andrea Orcel saying there had.

UniCredit is awaiting the European Central Bank approval it needs for the 28% stake it has built in the German lender, for the most part using derivatives.

"The approach of unilaterally building up and expanding a significant stake can only be considered as hostile," Commerzbank said in a statement.

UniCredit had announced an initial 9% stake in Commerzbank in September, angering the German government.

Speaking in Davos on Tuesday, Orcel said the backlash had come as a surprise, but that he hoped to be able to sit down with the future government formed after the Feb. 23 election to discuss a Commerzbank tie-up with HVB, the Bavarian bank UniCredit bought in 2005.

"HVB and Commerzbank have been talking to each other in both directions for over 20 years, because it's one of those deals that you always want to do, it makes a ton of sense, but for some reason it's always derailed," Orcel told Bloomberg TV.

"In the last two-and-a-half years we probably have had, and I probably have had, meetings with both the leadership of the government and the leadership of Commerzbank in the tens."

Asked to respond to Orcel's comments, Commerzbank said any talks could only be based on a specific proposal.

"We have consistently signalled our willingness to engage in discussions and would review a proposal from UniCredit in the interest of all stakeholders. However, we have not received any proposal yet," it said.

"UniCredit's approach has unnecessarily antagonised many stakeholders at our end, and Commerzbank's management must ensure that it continues to protect the interest of shareholders and the company in the best possible way."

On Wednesday, Orcel told the German paper FAZ he hoped for some clarity by the end of the year on UniCredit's strategy in Germany, once it had engaged with the future government.

Orcel has said any specific takeover offer must wait because of German rules that require a bid to be made in cash, with a floor for the price, if it comes within six months of crossing a 5% ownership threshold.