MILAN (Reuters) -The European Central Bank has given UniCredit approval to buy up to 29.9% of Commerzbank, the Italian bank said on Friday, potentially paving the way for CEO Andrea Orcel to pursue a takeover of Germany's second-biggest listed bank.

ECB approval was expected given UniCredit's financial strength and a supervisory stance which is supportive of consolidation efforts, but it still marks an important step towards what could become Europe's biggest cross-border banking deal since the global financial crisis.

UniCredit said it was likely to wait well beyond 2025 before making a decision on whether to proceed with an acquisition.

UniCredit's ambitions over Commerzbank date back to 2001, even before its 2005 acquisition of Munich-based HVB.

After failed attempts by his predecessors to grow UniCredit's footprint in the euro zone's biggest economy, Orcel in September stunned Berlin by snapping up shares in Commerzbank, before accumulating the right to own 28% of the bank through derivatives.

UniCredit said it needed a green light from Germany's competition authority before converting the derivatives into shares.

The German government and Commerzbank's management have both pledged to try and stop any takeover of the Frankfurt-based lender Berlin rescued in 2009.