Christofias said "now [was] not the time'' to say whether he was pleased with the talks and that he could not "predict anything with any certainty".
The two men are expected to continue to meet at least once a week in a bid to find a settlement.
Top of the list for discussion was the structure of a reunited Cyprus and how the Greek Cypriot majority would share power with the minority Turkish Cypriots.
The island has been divided since 1974 when Turkish forces invaded the north after the Cyprus National Guard mounted a coup aimed at unifying the island with Greece.
The European Union has made reunification essential to Turkey's bid to join the bloc.
On Wednesday, Taye-Brook Zerihoun, the UN chief of mission in Cyprus, said: "The complex and challenging process of finding a negotiated settlement of the Cyprus problem has started in earnest.
"Pursuit of the greater good of the people of Cyprus is key to overcoming past rancour and division, and in ushering in a new era of co-operation, prosperity and peace based on respect for diversity and shared principles."
But the issues of security, territory and Turkish settlers have held up any settlement.
Turkey has always insisted on retaining the right to intervene under the treaties signed with Britain and Greece that gave the island independence in 1960, and it retains at least 30,000 troops on the island.
Greek Cypriots want to drop the intervention rights, saying Cyprus should be free of all foreign troops, although Christofias has said he is willing to compromise on the issue of Turkish settlers on Cyprus by allowing 50,000 Turks to remain.
The negotiations, which initially began on September 3, mark the first major push for peace since the failure of a UN plan in 2004 when Turkish Cypriots accepted a UN peace plan which was rejected by Greek Cypriots.
Talat has expressed hope for a solution as soon as possible.
"My vision was to finish the negotiations by the end of this year and I believe it is possible," he said in Brussels on Wednesday.
But a poll of 600 people in the Greek Cypriot newspaper Simerini on Sunday found that 60 per cent believed the leaders would not reach an agreement, and 41 per cent thought the conflict would never be resolved.