He said this at a joint press conference after the EU-Ukraine summit, which took place in Brussels on Monday, a UKRINFORM correspondent reported.
"Agreements on the establishment of a deep and comprehensive free trade area between the EU and Ukraine contain obligations that need to be fulfilled. We discussed this issue with President [Viktor] Yanukovych today. Our positions were clearly defined... One country cannot at the same time be a member of a customs union and be in a deep common free-trade area with the European Union. This is not possible," Barroso said.
However, he noted that there are "some pragmatic ways to address this issue."
"And we have to respect the position of Ukraine," Barroso said, adding that Kyiv and Brussels have a common goal of political association and economic integration.