The Basel Committee made up of regulators from nearly 30 countries has come under intense pressure from the banking industry and European governments to rein in the reforms it is now completing, reports Reuters.
"Why are we doing this work? It's not to increase capital," Basel Committee Secretary-General William Coen said before a two-day committee meeting starting on Wednesday.
"If we wanted to increase capital, then that is far easier than what we are doing at present," he told reporters.
Coen said the changes were designed to prevent the wide variations in the way banks use models to assign risk weightings to assets such as loans, which in turn determines how much capital the lenders should hold.
But banks have dubbed the new rules "Basel IV", or a step change in capital requirements compared with the Basel III global framework put in place after taxpayers had to rescue banks during the 2007-09 financial crisis.
Deutsche Bank has said "Basel IV" unsettles investors and makes it difficult for banks to plan ahead.
The Basel Committee has said lenders should wait until the final rules are published, and Coen hinted on Tuesday that changes were likely as the committee typically revisits proposals in light of public consultations and field testing.
"This is the way the process is unfolding," Coen said.
Regulators suspect "outliers" - banks whose risk weightings diverge considerably from the industry average - are manipulating the models they use to assess risk to trim their own capital requirements.
Coen said the planned changes would restore confidence both in bank capital ratios and in the rules themselves.
The European Union, however, is worried the new rules could lead to a big increase in capital requirements for its banks whose lending is the major source of funding for the economy.
Basel's oversight body said on Sunday the work on the new rules was going in the right direction and it had reminded the committee of the need to ensure no significant increase in overall capital.
There is, however, no set definition of what this means, and while some big banks may face increases in capital requirements, many will likely see little change.
The reforms, which complete Basel's post-crisis revamp of its capital rules, cover elements such as risks from credit or loans, that make up the bulk of a bank's capital requirements.
Basel has yet to debate when the rule changes would come into effect. A 2019 deadline is seen as the earliest possible, while a later date may be more likely.