The rating agency Standard & Poor's on Friday affirmed Greece's sovereign debt rating at CCC+. The outlook remained stable.

The agency warned that it will downgrades the country's rating if the government does not implement reforms.

"We could lower the ratings on Greece if the new government cannot implement the reforms it has agreed to in the Memorandum of Understanding signed with the European Commission," Standard & Poor's said.

Greece will elect the new parliament on September 20.

The agency expect the Greece's economy to contract 3% this year.