* Requirements for top banks could be 3 pct points higher
* New rules would come on top of Basel III-sources
* Talks at early stage-sources
FRANKFURT, Oct 1 (Reuters) - Banks considered too big to fail could soon be held to even stricter capital requirements than those in the global Basel III package, sources told Reuters on Friday.
As part of new rules mooted by central bank governors and regulators, large international lenders would have to retain an equity buffer of up to 3 percentage points above the minimum rates agreed last month, regulatory and financial sources said.
"A mark-up in the region of 2 to 3 percentage points is realistic," said one of the people with knowledge of the matter.
Disagreement remains over which banks would plunge global markets into turbulence if they folded and should therefore set aside more equity capital and the plans are at an early stage.
While the inclusion of Germany's biggest lender Deutsche Bank is all but certain there are doubts whether the country's No.2, Commerzbank, would fit the criteria, sources in Germany said.
A main concern is that the fewer institutions that fall under the stricter rules, the bigger the risk of putting them at a competitive disadvantage against smaller rivals.
Global financial regulators finalised a package on Sept. 12 that will force banks to more than triple to 7 percent the amount of top quality capital they must hold to withstand shocks without state aid.
Leaders of the Group of 20 countries (G20), which called for last month's reform, are due to give final approval to the Basel III package in November.
The sources said that Germany did not oppose stricter rules for top banks, denying a report by TV channel CNBC on Thursday.
European Central Bank Governing Council member Axel Weber on Friday said the Financial Stability Board -- tasked by the G20 with drafting proposals to avoid a repeat of the financial crisis -- was in ongoing consultations about higher requirements for large banks.
The board was looking into a range of suggestions, he added.
(Reporting by: Andreas Framke, Philipp Halstrick and Ilona Wissenbach; Writing by Ludwig Burger)