By Oana Lungescu
BBC correspondent in Strasbourg
The European parliament is expected to approve the admission of Bulgaria and Romania to the European Union on Wednesday.
Both countries will be monitored
The decision will pave the way for the signing of an accession treaty later this month.
Both countries are set to join the EU in 2007.
But their memberships could be delayed by one year if they fail to make key reforms, such as curbing corruption and reorganising farming.
At last the EU seems within reach for Bulgaria and Romania, which missed the first big wave of expansion into the former Communist bloc last year.
Many European deputies think that Romania - a country of 23 million people - is still lagging behind.
But the European Enlargement Commissioner, Olli Rehn, called for cautious optimism.
The new Romanian centre-right government, he said, was tackling judicial reform and state subsidies and stepping up the fight against corruption.
However, he warned he would not hesitate to recommend delaying both countries' entry by one year if they proved unprepared.
Later this month, EU foreign ministers and their Romanian and Bulgarian counterparts will sign an accession treaty, which has to be ratified by national parliaments across the European Union.
For the next year and a half, both countries will be kept under close watch.