DUESSELDORF/FRANKFURT-Deutsche Bank is poised to swoop on rival Postbank in a two-part takeover valuing the retail lender at roughly $13 billion, sources with direct knowledge of the matter said.

It is set to be the second bumper all-German banking deal in as many weeks after Commerzbank bought Dresdner.

Two sources familiar with the matter said that Deutsche Bank would buy an initial stake of 29.75 percent in Postbank for about 57 euros per share from its postal group owner Deutsche Post.

Keeping its holding below 30 percent means Deutsche Bank does not have to launch a full takeover now. The plan, set to be blessed at a Deutsche Post supervisory board meeting on Friday, is to acquire more shares from Deutsche Post later.

Shares in Postbank came off early highs to trade at 46.40 euros while Deutsche Post shareholders also took heart at the prospect of a payout from the sale of the bank, sending its stock up 2.4 percent.

Deutsche Bank's move comes in the wake of investor frustration with the group's overdependence on its now-flagging investment bank. They have been pushing for a stronger retail bank to counter the boom and bust of Wall Street.

A takeover of Postbank, which Deutsche Bank Chief Executive Josef Ackermann turned down before its 2004 stock market listing at 28.50 euros a share, also keeps Spain's Santander, which was also stalking Postbank, off its doorstep in Germany.

JP Morgan said that the deal made little strategic sense and was a defensive move to block Santander. "Deutsche Bank would not be interested in having Santander and Postbank in their backyard," its analysts wrote in a note.

It is unclear how Deutsche will pay for the deal. It has been stretched as its bill from the financial crisis swelled beyond $11 billion, putting it among the top 10 global casualties of the turmoil.

Deutsche Bank has almost 1,000 branches in Germany, while Deutsche Postbank has 850 of its own branches plus access to thousands of post offices where it sells services.