Reuters) -Investment management firm Invesco Ltd is in talks to merge with State Street Corp’s asset-management business, a source familiar with the matter told Reuters on Thursday. The discussions between both the companies are at an early stage, the source added.It isn"t clear what the terms of a potential deal would look like, but it would be one of the industry"s biggest in recent memory, given that State Street"s asset-management unit manages nearly $4 trillion in assets, according to the Wall Street Journal that first reported on.wsj.com/3Ak1uv5 the development. Invesco declined to comment, while State Street did not immediately respond to a Reuters request for comment.The news follows State Street’s deal announcement last week to buy investment bank Brown Brothers Harriman & Co’s (BBH) investor services business for $3.5 billion. Shares of Invesco, which has $1.5 trillion in assets under management, rose 6.5% in extended trade, while State Street was up 2%.