Standard & Poor's on Wednesday downgraded Spain's longterm credit-rating by one notch to double-A with a negative outlook, just one day after roiling global markets with downgrades for both Greece and Portugal.

The ratings agency said that the Spain is likely to have an extended period of subdued economic growth, which weakens its budgetary position. The move sent equities in Spain the US broadly lower, while the euro fell back to a one-year low against the dollar of $1.3131.