Greek debt rating downgraded by Fitch

International rating agency Fitch has lowered the credit rating for Greece over concerns the country will not be able to handle its mounting debt.

Fitch cut Greece's ratings to Triple B-minus from Triple B-plus with a negative outlook and signaled more downgrades were possible. Fitch adds that it believes Athens will tap an external support mechanism agreed on last month by Euro zone leaders.

The package is a potential safety net that would include support from the International Monetary Fund. But Fitch says a lack of clarity on the deal's details may have hindered Greece's access to markets and hurt its chances of meeting its fiscal targets.