Finnish Prime Minister Matti Vanhanen said he expected the EU executive to put forward recommendations in the first week of December and EU foreign ministers to take a decision on December 11.
"The real deadline is before the Commission presents its recommendations," Vanhanen said in a speech.
EU Enlargement Commissioner Olli Rehn said December 6 was "the logical date" for the Commission to recommend consequences if Turkey had not met its obligation under an EU customs union to open Turkish ports to shipping from Cyprus.
Finland's proposal aims to allow direct trade with northern Cyprus and open Turkish ports and airports to Cypriot vessels and planes.
Turkey has said it will only open its ports if the EU acts to end the economic isolation of the Turkish Cypriot north of the divided Mediterranean island.
Diplomats expect a push on the issue when Finland hosts a meeting early next week of EU and Mediterranean foreign ministers, including Turkey's Abdullah Gul.
Vanhanen said he had no intention of letting the Turkey issue go on to an EU summit on December 14-15..
In a warning to Ankara, he said: "If there is no agreement and Turkey does not honour its commitments, the EU will need to consider the implications for the accession process. This is not a good scenario and it would mean an uncertain future."
WILLING NEGOTIATORS
Vanhanen said all the parties were willing to negotiate.
"No one has come up with an alternative solution or said that our proposal is unacceptable. We are all on the same page. Therefore the presidency still believes that a solution is possible."
Possible repercussions for Turkey if it fails to open its ports range from partial suspension of talks on joining the EU to a freeze in negotiations.
Vanhanen said the Finnish plan contained a limited number of proposals, and it was still up to the United Nations to try to reach a comprehensive settlement of the Cyprus issue.
U.N. Secretary-General Kofi Annan met Turkish Cypriot leader Mehmet Ali Talat in Geneva on Monday, after the world body proposed there should be a gradual build-up of talks between Greek and Turkish Cypriots to try to ease deadlock between them.
Talat said after meeting the outgoing U.N. chief that the Turkish Cypriots were ready for an unconditional resumption of negotiations with the Greek Cypriots on reunifying the island.
But he said any solution must be based on a detailed plan put forward by Annan in 2004 and could not be achieved by the EU.
"The EU is not an impartial, honest broker. It cannot be, because the Greek Cypriots and the Greeks are members," Talat told a news conference.
"Therefore a solution to the Cyprus problem will be definitely through the U.N. and not through the EU."
Turkish Cypriots voted in favour of a U.N. plan to reunite Cyprus in 2004 but the scheme foundered on Greek Cypriot opposition. The Greek Cypriots soon afterwards entered the EU as the sole legal representative of the island.
