'I think that our final conclusions probably will be drawn early after Easter, so it depends whether the measures then are still in place,' said Hans van den Broek, the Commissioner.
Emphasising the seriousness of the case against Greece, he said after meeting the Socialist Prime Minister, Andre as Papandreou: 'It is not an easy message that we carry.'
He gave no specific date or deadline for when the Commission might forward the case - against the current president of the EU - to the European Court.
Greece was told bluntly to lift the embargo or risk being dragged before the European Court in Luxembourg during a weekend EU foreign ministers' meeting, in the northern town of Ioannina.
'Everything has been discussed and weighed,' Mr van den Broek said. 'The foreign ministers in Ioannina have discussed this, and the conclusion there certainly is that these measures are very difficult (to see within the context of EU law). The Commission has in this respect a responsibility to take.'
Mr van den Broek insisted Greece's partners would try to help to solve a two-year dispute with the neighbouring republic, but said Athens must first lift its embargo.
The Commissioner's mission coincides with a visit to Athens by a new United States envoy, Matthew Nimitz, assigned by President Bill Clinton to help the UN mediate in the dispute.
Washington has criticised Greece for the embargo on the new Balkan state of some 2 million Slavs and ethnic Albanians on its border. Mr Papandreou has an unpleasant choice of ignoring his EU partners, or accepting an embarrassing climbdown which could hurt him politically at home.
The sanctions have been popular in Greece. Opinion polls show about 80 per cent of the public support them.
Greece imposed the embargo on 16 February to try to force Macedonia to make concessions before resuming UN- sponsored talks, broken off after Mr Papandreou won elections last October.
The embargo bars Skopje, the capital of the new republic, from using Greece's northern port of Salonika, through which some 80 per cent of its trade usually passes.
Athens wants the republic to change its name to prove it has no territorial ambitions on Greece's province of Macedonia, home of 2.5 million Greek Macedonians. It wants the republic to change its flag and rewrite its constitution.Reuse content