EU Enlargement Commissioner Olli Rehn was expected to give his preliminary assessment on Bulgaria and Romania's progress to join the EU late on Monday evening.
The two countries' readiness could be postponed from 2007 if they fail to make the grade.
Behind closed doors in Strasbourg, Rehn was expected to give MEPs in the foreign affairs committee a preliminary assessment of Bulgaria and Romania's readiness to join the EU at the beginning of next year.
This assessment will give an important indication of commission thinking just in the month before the Brussels executive is due to publish a report on both countries.
The "final report", which will recommend that the two countries join in January 2007 or push the date back a year, would be made public May 16.
The final decision about when Bulgaria and Romania will join has to be taken by the EU 25 and that will probably happen when EU leaders meet in June.
Sofia and Bucharest signed agreements in 2004 to join the EU but their entry into the bloc can be postponed if they are judged to be too far behind in making reforms.
With the countdown on, Bulgaria amended its constitution last Wednesday to improve its judiciary system, which is frequently criticised for being to slow and inefficient.
"We are living critical days as regards Bulgaria's preparation for accession," Rehn has said.