In September, the Basel Committee on Banking Supervision announced new standards to raise required common equity ratios to 7% by 2019, and have regulators implement the new capital rules by 2013.

Observers said that while the real work in crafting the Basel rules is the domain of the Basel committee, an official sign-off from the G-20 is still significant. The Seoul meeting officially begins Thursday.

"The G-20 ultimately is very important in this. We're talking about the key leaders in the entire world," said Douglas Elliott, a fellow at the Brookings Institution. "They told the Basel committee a little over a year ago to do this. It's now important for them to endorse this. This is old news but a very important event."

Karen Shaw Petrou, managing partner of Federal Financial Analytics Inc., said the G-20's official approval will "endorse a lot of hard work that has gone on in the last couple of months in the Basel committee."

A more contentious issue may be international coordination on dealing with "too big to fail."

While the Federal Deposit Insurance Corp. is currently implementing new resolution powers — mandated by the Dodd-Frank regulatory reform law — for systemically important firms in the U.S., world governments are still trying to agree on a common approach for winding down globally connected companies.

In October, the Financial Stability Board said it planned to recommend to G-20 leaders a "policy framework, work processes and time lines to address the 'too big to fail' problem associated with systemically important financial institutions."

The framework says, among other policy goals, that jurisdictions should be able to resolve firms "without disruption to the financial system and without taxpayer support," and large firms should have a "higher loss-absorbency capacity."

Observers said the G-20 meetings may produce general statements about the need for better coordination, but perhaps not much more.

Elliott said the farthest leaders may go is simply to support the work of the FSB and other groups studying the issue.

"I do think it will come up, but we're nowhere near having answers for it," he said. "They will undoubtedly endorse the direction of the analysis being done. But there isn't a package for them to endorse or turn down. We're not near that."

Elliott suggested the group may broadly endorse how the U.S. is tacking the issue. "I think they'll basically say, 'You're heading in the right general direction. Keep going.,'" he said.

Petrou said the U.S. is "marching ahead on a systemic and a resolution framework that will not be paralleled in the global arena."

"You will see the communique firmly for things like bank safety and not having banks that are 'too big to fail' and there being taxpayer risk, without any real agreement on what it is they're going to do," she said.