NEW YORK (Reuters) - Standard & Poor's will likely downgrade Greece's ratings to "selective default" when the country concludes its debt restructuring, but that will not necessarily destroy the credibility of the European Union, an official with the ratings agency said on Tuesday.

"It's not a given that Greece's default would have a domino effect in the euro zone," John Chambers, the chairman of S&P's sovereign rating committee, said in an event organized by Blooomberg Link.

(Reporting By Walter Brandimarte, Daniel Bases and Steven C. Johnson)