“There is concern among the banks that the stress test has led to uncertainty, the opposite of what is intended, and they would be diluting their shareholders based on a scenario that the regulators say themselves are unlikely to happen,” said Edward L. Yingling, the head of the American Bankers Association.

According to people briefed on the situation, the disputes center on several assumptions that regulators made in administering the tests. These include the severity of losses on assets like mortgages, credit card loans and commercial real estate loans, as well as the banks’ potential to generate earnings.

In a further challenge, the banks are also pushing regulators to relax the timetable for them to obtain new capital.

Some investors are prepared to buy problem assets from banks. What is less certain is whether banks will be willing to sell. Big money managers like BlackRock and Bank of New York Mellon said they had applied to raise money for the troubled-asset funds. While administration officials say they never expected every bank to participate, large banks whose involvement was regarded as vital to the plan’s success have said they will not be involved. Executives worry that whatever assurances the White House gives them, an angry Congress might impose new rules on banks that participate, particularly on pay.

Officials from Citigroup, Morgan Stanley, PNC Financial and a number of other big lenders that have received multibillion-dollar government bailouts are reluctant to participate or have refused so far to commit until more details are offered. Jamie Dimon, JPMorgan Chase’s chief executive, has said he believes that the Public-Private Investment Program  which depends on loans from the Federal Deposit Insurance Corporation  could be “good for the system” but that his bank has no intention of being either a seller or buyer. “We’re certainly not going to borrow from the federal government, because we’ve learned our lesson about that,” he said earlier this month in a conference about earnings.

Many banks are reluctant to sell their nonperforming loans because they could suffer big losses, forcing them to raise more capital. Others want to avoid the stigma of latching on to another federal program.

“Never mind the price,” James E. Rohr, PNC’s chief, said in a recent interview. “I wouldn’t want to be the first person and be perceived as a weak bank.”