FRANKFURT, April 29 (Reuters) - Deutsche Bank has said it could be on the hook for up to 1.3 billion euros ($1.39 billion) in claims from a long-running lawsuit alleging it underpaid shareholders for its purchase of retail banking division Postbank.

The following is a timeline of Deutsche's tumultuous history with Postbank, which has millions of clients and roots in the country's postal system.

2004

Deutsche Bank and Postbank sign an agreement on payment transactions.

2006

Deutsche's CEO Josef Ackermann says the bank is not interested in buying Postbank.

2007

Ackermann signals he may be interested in buying Postbank, saying he will "rule out absolutely nothing".

2008

Deutsche says it will buy Postbank in a two-stage manoeuvre, taking an initial stake of less than 30% with an option to launch a full-blown takeover later.

2010

Deutsche Bank says it plans to raise billions in capital to buy the rest of Postbank.

German financial publisher and Postbank shareholder Effecten-Spiegel says it is suing Deutsche for its lowball takeover offer for Postbank.

2011-2012

The Effecten-Spiegel case bounces around regional and higher courts.

2014

More former Postbank shareholders sue over the Postbank takeover.

2015

In a u-turn, Deutsche announces plans to sell Postbank.

2016

In yet another u-turn, Deutsche considers opting for a full integration of Postbank instead of a sale.

2017

Deutsche scraps plans to sell Postbank.

A judge says there is no evidence of wrongdoing by Deutsche in its Postbank purchase.

2018

International and German investors sue Deutsche Bank for 740 million euros in connection with its takeover of Postbank.

Deutsche merges with Postbank, creating a bank with 20 million private clients and one million business and corporate customers.

2020

A German court rules that Deutsche Bank does not have to pay former Postbank investors higher compensation than offered in its 2010 tender offer. The plaintiffs appeal.

2022

A high court sends a Postbank investor case back to a regional court.

2023

July 3 - Deutsche says it has completed a fourth and final phase of a years-long technology integration process with Postbank.

Sept. 20 - Deutsche has disappointed customers with service lapses at Postbank and is devoting additional resources to quickly regain trust, the lender's CEO says.

Oct 2. - Germany's top financial regulator appoints a supervisor to Deutsche to assess customer service after the Postbank integration left clients complaining they were locked out of their accounts and unable to reach call centres.

Dec. 20 - Deutsche says efforts to resolve consumer complaints at its Postbank unit will continue into 2024, taking longer than previously anticipated.

2024

April 10 - A months-long wage dispute at Deutsche Bank's Postbank arm escalates with additional strikes as employees demand a 15.5% pay raise.

April 17 - A fourth round of wage talks for Postbank staff fails.

April 26 - Deutsche says it will make a legal provision in the Postbank suit that will hurt second-quarter and full-year earnings.

April 29 - Deutsche shares fall sharply after the news of the provision. ($1 = 0.9343 euros) (Reporting by Tom Sims; Editing by Jan Harvey)