Fitch ratings agency is warning of a possible downgrade of Greek bonds, adding pressure on the Socialist government as it debates the 2011 budget in parliament.

Fitch said Tuesday that the action “indicates that there is a heightened probability that Greece’s sovereign ratings will be downgraded” from its current BBB-status after a review is completed next month.

It follows similar warnings from ratings agencies Moody’s and Standard and Poor’s earlier in December.

The government is facing increasing hostility from unions, opposition parties and even the Greek Orthodox Church and skeptics within its own party over austerity measures.

Parliament is due to vote on the budget late Wednesday.