Together with other high-ranking EU officials Solana arrived in Ukraine for the ninth EU-Ukraine summit on Friday.
He said Ukraine should reconsider holding the constitutional reform to establish an efficient system of checks and balances and strengthen governmental institutions since the 2004 reform failed to delimit powers between government departments.
The EU official said the political crises Ukraine had seen in the past few years were mostly caused by a lack of transparency in major political rules.
Though Solana doubted if early parliamentary elections scheduled for September 30 would solve all political problems in Ukraine, he said this was a nice instrument for surveying public opinion regarding where the country should move and who should be its leader.
However, the lack of international stability in Ukraine almost did not affect the negotiations on signing a new Enhanced Agreement between the European Union and Ukraine, which Solana said was a convincing proof that all political forces in Ukraine favored integration into the EU.
Ukrainian President Viktor Yushchenko issued three decrees dissolving parliament in spring after 11 opposition members defected to the ruling coalition, bringing it closer to a 300-member majority able to override presidential vetoes.
The president's decrees were challenged by the Supreme Rada and eventually his longtime rival, pro-Russian Prime Minister Viktor Yanukovych, struck a deal to hold early parliamentary elections on September 30 in a bid to end months of political wrangling.