Standard & Poor's on Tuesday said there is a greater number of sovereign and banking bonds at risk of ratings downgrades as a result of its recent warning that it might cut the credit ratings on 15 euro zone nations.

"Sovereigns and banks continue to show the greatest downgrade risk. The entities in these two sectors are concentrated in Europe, with 25 European sovereigns and 42 European banks on our potential bond downgrades list," Diane Vazza, head of Standard & Poor's global fixed income research, said in a statement.

S&P said it listed 463 entities as most at risk of downgrades as of Dec. 6, up from 457 on Nov. 1.

On Dec. 5, S&P placed the ratings of 15 euro zone countries on credit watch negative -- including those of top-rated Germany and France, the region's two biggest economies -- and said "systemic stresses" are building up as credit conditions tighten in the 17-nation region.

The warning came before leaders of 26 European Union nations reached a historic agreement last week to draft a new treaty for deeper integration in the euro zone in an effort to rein in the region's debt crisis.

Although a credit watch negative review typically means there will be a decision within three months, S&P last week had said that it would conclude its review "as soon as possible" following the EU leaders summit.

S&P on Tuesday said that since its last report, it had removed 74 entities from its potential downgrades list and added 80.

"Of the issuers that we removed from the potential downgrades list since our last report, 12 are in the banking sector. Seven of the 12 banks were downgraded, most of them in Europe, which reflects ongoing economic concerns in the euro zone," S&P said in its statement.

Markets remain on edge over what S&P's decision will be on the euro zone ratings. Will they find enough in the new treaty to hold off on a downgrade, be satisfied the new treaty is moving the region in the right direction? Or is the agreement not enough to change S&P's opinion that the credit crisis is being solved in a proficient manner?

On Monday, S&P's chief economist Jean-Michel Six said time was running out for the single currency bloc to resolve its debt problems.

"There is probably yet another shock required before everybody in the euro zone reads from the same page, for instance a major German bank experiencing some real difficulties on the markets, which is a genuine possibility in the near term," Six told a business conference in Tel Aviv. (Additional reporting Caryn Trokie; Editing by Leslie Adler)