The private-equity firm leading the proposed buyout of Sallie Mae has come back with a new offer for the student-loan giant.

The firm, J.C. Flowers & Company of New York City, canceled the $25-billion takeover plan last week, saying that Congress had cut federal subsidies to student-loan providers more deeply than the company was willing to accept.

Flowers said its decision was consistent with the $60-per-share purchase agreement it announced in April, which allowed Flowers to call off the deal with Sallie Mae if Congress approved subsidy cuts more costly than those proposed by President Bush.

In its new buyout proposal today, Flowers said it disputed Sallie Mae’s interpretation both of the April contract and of the severity of the effect of the federal-subsidy cuts approved last month by Congress. Flowers said it was now willing to offer at least $50 a share for Sallie Mae, along with a commitment to increase that price if Sallie Mae met certain performance goals.

Flowers said that if Sallie Mae met the profit levels it still predicts for the company, the net price would end up at about $57 a share. If Sallie Mae exceeded its own projections, it could still end up realizing the original $60-per-share price.

Sallie Mae, whose formal name is the SLM Corporation, posted a statement on its Web site today saying it expected the proposed buyers, which also include Bank of America and JPMorgan Chase, to honor their contract. —Paul Basken