S&P-- Euro Zone on Watch for a Ratings Downgrade.

Asian shares declined Tuesday, with investors unsettled after Standard & Poor’s placed most of the euro zone on watch for a ratings downgrade.

Wall Street stocks also ended higher, but were off their best levels of the day after reports — only later confirmed — that S&P had placed the sovereign ratings of 15 euro-zone countries on watch for a possible downgrade in the next 90 days.

Positive European developments on the weekend and early Monday “were destroyed” by the S&P news, said strategists at BNP Paribas.