After several months of review, Moody's (NYSE: MCO) has maintained its rating of Baa3 -- its lowest level of investment grade -- on Spain's government bonds, it announced in a press release yesterday. However, the agency introduced a negative outlook to that score.

The press release explained that the decision to keep the debt-plagued nation at investment grade status was due to the demonstrated willingness of the European Central Bank to buy those bonds in order to alleviate price volatility, and the likelihood that the country will apply for a credit line from the European Union's Financial Stability Mechanism. Other reasons cited were the government's efforts to implement fiscal and structural reforms, and its progress in supporting and restructuring domestic banks.

Moody's added that it introduced its negative outlook because overall risk remains high for Spain.

According to a Reuters report, the reaffirmed rating broadly matches those from the other two of the "big three" rating agencies; Fitch currently grades Spanish government bonds a BBB with a negative outlook, while Standard & Poor's rates them a straight BBB-minus.