The announcement lent momentum to a campaign by France and Italy to reimpose some of the border checks, abolished in 1995 under the Schengen agreement, as they grapple with an influx of migrants fleeing political upheaval in North Africa.
In a letter to Italian Prime Minister Silvio Berlusconi and French President Nicolas Sarkozy, José Manuel Barroso, president of the European Commission, said it would be possible to permit countries to reintroduce limited controls.
"The temporary restoration of borders is one of the possibilities, provided this is subject to specific and clearly defined criteria, that could be an element to strengthen the governance of the Schengen agreement," Barroso wrote.
EU countries may already introduce temporary border checks as Germany has done to stop foreign soccer hooligans visiting football games, but new EU rules could widen countries' freedom to do so, said a source familiar with the plans.
"To reinstate border controls now, you have to justify that based on the threat to public order," said one EU source.
"With the new system, you would no longer need to invoke a threat to public order. This would extend the possibilities to reinstate controls."
Reinforced partnership with South Mediterranean
Beyond the possibility of reinstating border checks, Barroso insists on strengthening relations with Mediterranean countries as an essential element of the EU's answer to the immigration crisis.
"The Commission considers that only a reinforced partnership with countries at the South of the Mediterranean will allow a sustainable solution to the current migratory pressure," Barroso wrote in his letter.
He also underlined the necessity to put in place a common asylum system, stressing that previous attempts were defeated due to resistance from EU member countries. He called on France and Italy to push for reforming the EU's asylum regime "before 2012".
The EU executive, which writes the first draft of EU laws that are then sent to countries for approval, plans to present an outline of its legal proposals on Wednesday (4 May). EU heads of state and government will discuss the proposals at a summit on 24 June.
If accepted, the new EU rules would alter one of the biggest achievements of the single European market, passport-free travel, but one which makes it harder to curb illegal migration.
The proposals could become law as soon as they are agreed by the EU's 27 member states and the bloc's parliament, a process that could be concluded in months but could also easily drag on for more than a year.
The arrival of thousands of immigrants from North Africa prompted France in April to shut its borders to trains carrying African migrants from Italy.
The two countries accused each other of flouting the spirit of the Schengen treaty, which eliminates many border controls within the EU.
So far this year, around 25,000 migrants, most from France's former colony Tunisia, have arrived in southern Italy on small, overloaded fishing boats, creating a humanitarian emergency on the tiny island of Lampedusa where most of the boats landed.
Italy says it has been left to deal with the problem on its own while Paris has accused Rome of trying to escape its responsibilities by allowing illegal immigrants free transit across the border. Last Tuesday, French President Sarkozy visited Rome to try to defuse tension.
(EurActiv with Reuters.)