A study by the World Economic Forum suggests most EU countries, including those due to join on 1 May, are lagging behind the US on competitiveness.
The loss of skilled young people could hit new EU members hard
The survey says four years after EU leaders agreed economic reforms to make the EU the most dynamic economy in the world by 2010, progress has been slow.
Only Nordic countries have managed to surpass the United States.
The WEF says on a number of measures of competitiveness, the average EU score, out of 7, is 4.97, and 5.55 for the US.
The top accession countries on this measure were Estonia and Slovenia, while the applicant countries of Romania and Bulgaria are at the bottom of the pile.
"Policy makers in Europe will have to focus their energies on accelerating the pace of reform," according to Dr Augusto Lopez-Claros, chief economist of the World Economic Forum.
Only Finland, Denmark and Sweden ranked higher than the US among the 25 EU members (as of 1 May).
TOP EU COUNTRIES BY COMPETITIVENESS
Source: World Economic Forum
Finland, whose largest company is the mobile phone firm Nokia, scored particularly highly on information society, innovation, and networking.
The Nordic countries also scored highly on social inclusion and sustainable development.
The UK, which came fourth after the Scandinavians, scored better on liberalisation and financial services, but lower on social inclusion and innovation.
Spain, Italy, Portugal and Greece were lowest among existing EU members on these measures.
But perhaps surprisingly, Italy, a G7 member, performed worse than Spain, and below Slovenia and Estonia, on several criteria.
Among the 10 accession countries, most scored at or below the level of Greece except for the Baltic countries, the Czech Republic, Hungary and Slovenia.
Poland, with the largest economy and population among those joining the EU, ranked 9th, just above Turkey, Romania and Bulgaria (Cyprus was not ranked).
But the report points out that the top accession countries are actually better prepared to compete than the worst three existing members - with the exception of telecoms liberalisation and completion of the single market.
The eight measures of competitiveness were: an information society for all; innovation and R&D; liberalisation of the single market; building network industries; creating efficient financial services; improving the enterprise culture; increasing social inclusion; and enhancing sustainable development.