Invesco Ltd is in discussions to acquire part of the investment management business of Guggenheim Partners LLC, including its exchange-traded funds (ETF) business, according to a person familiar with the matter.

The discussions are fluid and a deal is not close to being finalized, according to the person, who was not authorized to discuss the matter publicly.

A spokesman for Guggenheim and a spokeswoman for Invesco each said they do not comment on market rumors.

Invesco, the world's fourth-largest ETF provider, has a history of making big deals. In April it acquired Europe-based asset manager Source, bolstering its ETF product lineup. The company managed $858 billion in assets as of June 30.

ETFs have been one of the fastest-growth products in asset management. They allow investors to trade an entire basket of stocks or bonds as easily as trading one stock. They often track a broad market index, instead of trying to outperform, and can be relatively low cost. Those factors have allowed the funds to win assets away from incumbent products.

Guggenheim Investments had positive net flows into all its actively managed taxable fixed-income mutual funds and ETFs in July and now has a firm-record $30 billion under management in its retail bond mutual funds and ETFs and a firm-record $180 billion in fixed-income assets under management overall, the company said on Tuesday.

Guggenheim has been disputing what the Financial Times last month called a "power struggle" between Chief Executive Officer Mark Walter and Global Chief Investment Officer Scott Minerd.

Todd Rosenbluth, directtor of mutual fund and ETF research at CFRA, said that the acquisition makes sense for both companies.

"While iShares, SSGA and Vanguard have the lion share of ETF assets, smart beta ETFs have increasingly gained in popularity with institutional and retail investors," said Rosenbluth. "Powershares and Guggenheim have some compelling, straight forward ETFs, including S&P 500 based SPLV and RSP, CFRA thinks such a combination could provide scale as newer deep pocketed ETF entrants, such as Goldman Sachs and JP Morgan, seek to gain smart beta market shares."

This article was provided by Reuters, with contribution from Financial Advisor associate editor Christopher Robbins