The Commission will propose that Slovenia and Estonia should join Poland, the Czech Republic, Hungary and Cyprus in the first wave of new member states.
The proposals will give existing EU leaders a clear choice when they come to finalise the list of new countries during a December meeting in Luxembourg.
The proposals, entitled "Agenda 2000", will also set out plans for major reform of EU policies on farming and aid for poor regions, paving the way for expansion.
The enlargement of the EU coincides with a parallel process occurring in Nato, as both organisations seek to end the old Cold War divisions. For the EU, the current expansion is the most challenging and potentially divisive yet undertaken. It is already causing more friction than the accession of Spain, Portugal and Greece in the 1980s.
The first six applicants (or "five-plus-one" as the group is known, distinguishing Cyprus from the East Europeans) may be full members by 2002. With a total of 10 applicants waiting to join, the expansion could ultimately lead to a European Union of half a billion people, stretching from the Arctic Circle to the Aegean, and from the Black Sea to the Atlantic Ocean.
The difficulties facing would-be members, as they seek to meet the EU's single-market standards, adopt agricultural norms, ensure democratic freedoms and apply EU policies on open borders and the environment, are far-reaching.
But the candidates seem determined to make the grade. For some would- be members, the economic benefit of the EU is now a higher priority than the military security of Nato membership. Nevertheless, the candidates are watching with some trepidation as evidence grows that political will to accept them may be lacking.
Britain has always backed enlargement, some would say because it is likely to dilute federalism. But some countries - such as Spain, Italy, Ireland and Greece - fear expansion, knowing it will divert aid from their own, poorer regions.
Commission proposals for reform of the common agricultural policy (CAP) have been drawn up with enlargement in mind; the idea is to take the burden off the taxpayer and help consumers.
Under plans for reforming structural funds, to be published next week, the Commission envisages a freeze on spending and an overhaul of priorities, which are certain to cause ructions, particularly in poorer southern countries. Even without enlargement, the plans mean a reduction in the number of EU citizens benefiting from structural funds from 51 to 31 per cent.
Germany, hitherto in the vanguard of the supporters of EU expansion, has developed increasingly cold feet due to fears that it will be asked to pay the bill.
The strictures of meeting the Maastricht criteria for the single currency have exacerbated fears about cost across the union.
Should Europe fail to set up a single currency by 1 January 1999, it is widely acknowledged that enlargement would be forced off its tracks.
France is only lukewarm, and French officials have recently questioned whether the EU has the "common vision" necessary to accept new members.
Smaller member states fear expansion will diminish their clout, shifting the balance of power as the new members wield their votes in the Council of Ministers.
The strongest evidence of a cooling towards the eastern neighbours came at the Amsterdam summit, when the existing 15 failed to agree even on mild reforms in readiness for enlargement.
Bitter divisions over expansion also emerged last week within the European Commission, when Jacques Santer, President of the European Commission, and several commissioners, urged restricting first-wave negotiations to Poland, the Czech Republic and Hungary.
Sir Leon Brittan, the trade commissioner, argued against a political fix, saying expert opinions justified Slovenia and Estonia joining too. In the end, the case for broader expansion won the day.
This decision may defuse doubts about the EU's commitment to proceed with enlargement. Had the smaller list been agreed at Commission level, the prospects of a broader enlargement being endorsed by member states would have been small, and accusations from candidates of political double- dealing would have been levelled against Brussels.