Standard & Poor's Ratings Services has only one reason to upgrade Greece's credit by 6 notches because all the other 16 European Union countries using the euro are determined to keep Greece inside the currency union (believes SP).

The statements came on Tuesday from the Ratings agency Standard & Poor's, which upgraded Greece's credit grade by 6 notches, thereby bringing it up from SD, or selective default and reaching it to B minus with a stable outlook.

Their decision has though yanked the debt-heavy country out of default; its devalued bonds are still in junk status. This upgrade to B- (B minus) is the highest grade that has been given so far by the agency to Greece since June
2011.

"The stable outlook balances our view of Eurozone member states' determination to support Greece's Eurozone membership and the Greek government's commitment to a fiscal and structural adjustment against the economic and political challenges of doing so", the agency said in a statement.

According to the reports, among all the three main agencies, S&P's rating for Greece is the highest with 6 notches whereas Fitch has rated it at one notch above default and Moody's has still listed the country in default. The upgrade has been warmly welcomed by the Greece's finance minister.