Citigroup Inc. is facing a unique dilemma among the four largest U.S. banks: it is light on deposits from individuals, an important funding source that costs little and tends to stick around.

While big rivals grew deposits dramatically after the 2007-2009 financial crisis from their broad networks of branches, Citigroup backed out of all but six U.S. cities and closed one-third of its branches.

The bank is now trying to up its game with a new app it plans to begin marketing in the third quarter. Executives hope it can lure deposits without opening new branches, acquiring a rival or beating competitors’ rates – three ways to collect deposits with their own costs and risks.

“People are willing to switch to a bank that is able to provide this kind of mobile-first experience,” David Chubak, head of global retail banking and mortgage, said in a statement, citing customer research Citigroup conducted.

The app, which does not have a name, will augment the bank’s push to expand its wealth management business, he said.

Competing for deposits is important as interest rates rise. When banks start reporting second-quarter results on Friday, investors will be closely watching deposit levels and what they cost.

The stakes are high for Citigroup, which is less profitable than rivals and trying to meet elusive financial targets set by Chief Executive Officer Michael Corbat.

Citigroup, the third-biggest U.S. bank by assets, has 4 percent of U.S. deposits, compared with about 11 percent at JPMorgan Chase & Co., Bank of America Corp. and Wells Fargo & Co., according to S&P Global.

Citigroup has more than enough to fund its loans, but its earns only one-third as much revenue from U.S. consumer deposits as JPMorgan and Bank of America do, said Peter Nerby, a bank analyst at Moody’s Investors Service.

That gap could widen as other banks carry out plans to expand into new cities by building hundreds of branches to go along with their own apps. Citigroup has 700 branches, compared with Bank of America’s 4,400 branches and JPMorgan’s 5,100.

“Digital offers can only get you so much,” Dean Athanasia, co-head of Bank of America’s consumer banking division, said in an interview.

Even as customers embrace digital apps, they still want a local branch where they can see someone, he said.

Citigroup may open branches selectively over time in locations where it would help its wealth business, Chuback said.