UPDATE 1-IIF chairman urges decisive action on Greek debt -CNBC

* IIF chairman says willing to talk on Greek debt-CNBC

* IIF wants more decisiveness on public sector side -CNBC

* IIF says ECB help crucial to calming banking system -CNBC

FRANKFURT, Jan 26 (Reuters) - The Institute of International Finance (IIF) wants public sector officials to be more decisive in negotiations over Greek debt, the bank lobby group's chairman and Deutsche Bank Chief Executive Josef Ackermann told CNBC on Thursday.

Upon being asked about Greek debt restructuring, Ackermann said: "(We) need someone on the public sector side who can really make (a) decision. We are getting closer to that, we are willing to negotiate. I think we have every interest to come to (a) solution in the next few days."

A disorderly default of Greece could imperil progress made in Portugal, Italy and Spain to bring down deficit levels, said Ackermann, who was speaking with CNBC at the World Economic Forum in Davos.

"We just have to be a little bit patient, and that's why a contagion impact from Greece would be so negative," Ackermann said.

"People are underestimating the collateral damage," the Swiss executive told the TV station. "At the end, of course, we need a bigger firewall in case there is contagion."

Moves by the European Central Bank (ECB) to prop up the banking system with liquidity are welcome, he said, but added that further steps to bring down debt levels were needed.

"The ECB move was crucial, very positive for the banking system, (since) it calmed down markets, but it is not the final solution, and we have to see that all of the countries are doing their homework so they can go back and raise funds in the market for themselves."

Deutsche Bank itself has limited direct exposure to Greek debt to the point where it is now "marginal". The Frankfurt-based lender is "very comfortable" about meeting new capital requirements by the European Banking Authority, he further said.

Upon being asked whether Deutsche Bank expects to need to raise capital this year, Ackermann told CNBC "absolutely not".

In a separate interview with German TV station Deutsches Anleger Fernsehen, also at the World Economic Forum on Thursday, Ackermann said: "I am confident everything is being done to prevent Greece becoming insolvent."

"We all need to make our contribution. The private sector is making its contribution. I too am doing everything I can," Ackermann said.

Deutsche Bank's CEO said the lender noticed some slowdown in its business compared to last January.

"The start was better than the end of last year, but not as good as a year ago," he said.