As fears of a default weighed on European and U.S. stock and bond markets, the European head of the International Monetary Fund (IMF) said on Friday that Greece’s growth projections will need to be "significantly" revised down from the estimate made last week that Greece's economy would grow by 2.5 percent this year and 3.7 percent in 2016.

Some analysts, aware of the country's hefty debt burden and deadlocked talk with international creditors, found this estimate to be highly unrealistic and Poul Thomsen, director of the IMF's European department, admitted on Friday that the forecasts were way off line.

According to Thomsen, "Our growth projection for this year will clearly have to be revised down significantly because of the current turmoil, because of the delay in completing the review. So once again, growth will underperform. “

Greece Likely to Default

The country is seen as increasingly likely to default on its debt obligations, as negotiations with its international bailout supervisors have failed to succeed in bringing about a further tranche of aid.

Greece's finance minister, Yanis Varoufakis, is currently in meetings with U.S. and IMF officials in Washington that could determine the country's economic future. The IMF is Greece's key creditor.

Another important meeting will take place on April 24, when euro zone finance ministers will meet to discuss Greece making economic and political reforms in return for more aid.

In the meantime, Greece fears were attributed to the drop in stocks and bonds down across Europe and in the U.S. on Friday.