Schuessel was speaking at the 2nd Crans Montana Forum, a big economic and political meeting that is being held in Zagreb's Westin hotel from Wednesday to Friday.
In his speech Schuessel recalled the different levels of integration with the EU of the countries in the region, stressing that the future of Southeast Europe lay in the EU, which he said the EU had confirmed with its firm intention to implement the Thessaloniki agenda.
Schuessel reiterated that the progress of every country depended on its individual progress and that some countries had already covered a large section of the road.
Mentioning each country in the region individually and the level of its integration with the EU, the Austrian Chancellor pointed to the need for regional cooperation.
He said that the situation in the EU today was better than one year ago and that there was no reason for pessimism regarding the southeast of Europe.
There is no reason for pessimism - the EU has opened talks with Croatia; Bulgaria and Romania are practically EU members, and Slovenia will become the first country in the region to enter the zone of the single European currency, Schuessel told the conference.
After Schuessel, the conference was addressed by Slovene President Janez Drnovsek, who said that the EU had to continue developing despite the situation which he said until recently was called a crisis.
The EU must find a way to adopt a new constitution because it will not be able to develop further without an institutional framework, he said.
"We need it for the sake of development, but also for the sake of enlargement because the EU must continue expanding, instead of hiding behind phrases about tiredness," Drnovsek said.
He said that Croatia was a good candidate for the EU, but warned that the rest of the region needed European prospects as there was no alternative to them.
Former Romanian president Ion Iliescu said that the EU had to solve two problems - consolidate its institutional framework and continue expanding. Europe must find a solution to both problems in order to survive and be capable of partnership with two big powers - the United State and Asian countries, Iliescu said, welcoming the EU's determination to continue enlargement.
Bosnian Prime Minister Adnan Terzic said that there were no problems between his country and Croatia, except for some outstanding issues that were the result of the break-up of the former federation, which he said required just a little time to solve. It is on the model of Croatia that Bosnia-Herzegovina is building its future towards a fully democratic and self-sustainable state, Terzic said.
Montenegrin Prime Minister Milo Djukanovic said Croatia set an example how the fulfilment of the set criteria rather than the size of a country determined its status, and congratulated Croatia on its success.
The Zagreb conference was previously addressed by the Special Coordinator of the Stability Pact for Southeastern Europe, Erhard Busek, and Macedonian Deputy Prime Minister Radmila Sekerinska.