Big Wall Street banks are so upset with U.S. Democratic Senator Elizabeth Warren's call for them to be broken up that some have discussed withholding campaign donations to Senate Democrats in symbolic protest, sources familiar with the discussions said.

Representatives from Citigroup, JPMorgan, Goldman Sachs and Bank of America, have met to discuss ways to urge Democrats, including Warren and Ohio Senator Sherrod Brown, to soften their party's tone toward Wall Street, sources familiar with the discussions said this week.

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Bank officials said the idea of withholding donations was not discussed at a meeting of the four banks in Washington but it has been raised in one-on-one conversations between representatives of some of them. However, there was no agreement on coordinating any action, and each bank is making its own decision, they said.

The amount of money at stake, a maximum of $15,000 per bank, means the gesture is symbolic rather than material Moreover, banks' hostility toward Warren, who is not a presidential candidate, will not have a direct impact on the presumed Democratic front runner in the White House race, Hillary Clinton. That's because their fund-raising groups focus on congressional races rather than the presidential election Still, political strategists say Clinton could struggle to raise money among Wall Street financiers who worry that Democrats are becoming less business friendly.

The tensions are a sign that the aftermath of the 2008 financial crisis—the bank bailouts and the fights over financial reforms to rein in Wall Street—are still a factor in the 2016 elections.