The European Commission said Tuesday it was considering giving Ukraine temporary relief on customs duties until Nov. 1, when both sides are expected to sign a comprehensive free trade agreement.
Barroso told members of the European Parliament in Strasbourg, France, financial assistance to a cash-strapped Ukraine was "not a quick fix" solution to the crisis.
"[It] needs to be complemented by ... a reform-oriented and inclusive Ukrainian government, committed to fixing the current state of their financial system and rebuilding the economic foundations of the country, during both the current transition phase and in the medium to long term," he said.
A Ukrainian decision in November to suspend efforts to sign free trade and association agreements with the European Union sparked widespread protests that led to the February ouster of President Viktor Yanukovych. A Kremlin ally, he said Yanukovych made the decision to protect Ukraine's economic ties to Russia.
Western leaders have reacted angrily over a Kremlin decision to send troops to Crimea, a pro-Kremlin peninsula in Ukraine where Russia's Black Sea naval fleet is based, following the ouster of Yanukovych.
"What happened in Crimea was an unprovoked and unacceptable violation of Ukrainian sovereignty and its territorial integrity," Barroso said.