The five other members of the group were in favour of the plan and saw no need for delay, he said.
Ahtisaari needs the approval of the group before he can make the plan public.
Diplomatic sources had said that the Vienna meeting was intended to be the last step before Ahtisaari presented his blueprint to officials in Pristina and Belgrade on February 2.
Serbs and Kosovo Albanians had been due to discuss the fine print of the deal next month, although there was little prospect of them reaching an agreement.
Eight years after Nato drove Serb forces out of the province, Kosovo is demanding nothing less than full independence.
|Ahtisaari was due to present his plan to |
Belgrade and Pristina on February 2 [AFP]
Meanwhile, Serbia is offering only far-reaching autonomy for a territory that it sees as the traditional birth-place of the Serb nation.
Ahtisaari said on Wednesday that his plan would focus on "the protection of minority rights, in particular of the Kosovo Serbs" and "a strong international civilian and military presence within a broader future international engagement in Kosovo."
Diplomatic and UN sources told Reuters that Kosovo would be given the right to apply for membership of international organisations, potentially including the United Nations, the International Monetary Fund and the World Bank.
They said it would provide for a right to dual citizenship, and urge Pristina to establish good relations with Serbia and other neighbours, but would contain no reference to Serbian sovereignty.
Germany, Britain, France, Italy and the United States have all said they believe that the Albanians should be granted self-determination, but Russia has said it would not back a solution that went against the wishes of Serbia.
Diplomats had said they felt that there was enough room for manoeuvre between the two positions to avoid a Russian veto in the UN Security Council later this year.
Nato countries, which have more than 16,000 peacekeepers in Kosovo, have vowed to maintain support for international efforts to resolve its status but called a rapid resolution.
James Appathurai, a Nato spokesman, said: "There was an enduring and unflagging commitment for Nato to play its part in the process related to status and beyond it.
"There was a strong sense around the table on the need for a resolution as soon as possible. Long delays risk a lack of clarity, risk fostering instability."