Swiss bank Vontobel Holding AG (VONN.EB) said Thursday it will buy Commerzbank AG's (CBK.XE) Swiss operations, which manage assets of around 4.5 billion Swiss francs ($4.17 billion).

"The Vontobel Group will strengthen its market presence in Switzerland while, at the same time, broadening its international client base," the Zurich-based bank said in a statement.

Financial details weren't disclosed. The deal will bolster Vontobel's private-banking assets by one-fifth to roughly CHF28 billion. The acquisition will also be good for the Vontobel unit's profitability, lowering the private-banking cost-to-income ratio by 2% to 4%, Vontobel said.

The deal is expected to close later this year with Commerzbank integrated by early 2010. As a result of the integration, the Commerzbank brand will eventually be replaced by Vontobel.

The transaction isn't the first sale for Germany's Commerzbank, which is attempting to shrink its balance sheet after the European Commission in May mandated it refinance its business model as a condition for receiving state aid.

Earlier this week, Commerzbank sold Dresdner Bank's Swiss asset-management business to Liechtenstein-based LGT Group, less than a year after acquired Dresdner from German insurer Allianz SE (AZ).

Commerzbank is tasked with repaying billions of euros in state aid and minimizing losses from an internal holding unit that it said in March contained more than EUR55 billion in toxic assets.

For Vontobel, which is paying an undisclosed amount of cash for the bank, the acquisition gives a much-needed shot in the arm to its private-banking unit. Analysts traditionally apply a discount to Vontobel compared with other Swiss banks because a higher proportion of revenue and profits come from investment banking, as opposed to less-risky money-management for the wealthy.

Commerzbank's Swiss arm is based in Zurich and has offices in Vienna and Geneva, where Vontobel also has offices.

Company Web site: www.vontobel.com

-By Katharina Bart, Dow Jones Newswires; +41 43 443 8043; katharina.bart@dowjones.com