A multibillion dollar dispute between the Environmental Protection Agency and several nonprofit organizations escalated on Saturday when one group sued the E.P.A. and Citibank, seeking access to a grant it had received during the Biden administration but has been frozen under President Trump.

Climate United, a nonprofit organization, claimed that the E.P.A. and Citibank have illegally withheld a nearly $7 billion award announced last April. Citibank has housed the funds as part of a green financing program to finance projects that address climate change.

The funds are part of a larger pot of money, $20 billion, that have been swept up in controversy after Lee Zeldin, the E.P.A. administrator, called the green financing program a “scheme” that was “purposely designed to obligate all of the money in a rush job with reduced oversight.”

Now, some of the nonprofits say, their bank accounts are frozen and that they are struggling to pay staff.

Climate United had planned to loan the money to developers across the country in support of solar power, electric trucks, and energy-efficient affordable housing projects, and said the freeze has meant small businesses and developers are unable to draw down funds they were promised.

“We’re not trying to make a political statement here,” said Beth Bafford, chief executive of Climate United. “This is about math for homeowners, for truck drivers, for public schools — we know that accessing clean energy saves them money that they can use on far more important things.”