Kiev also blamed the International Monetary Fund for imposing stringent conditions for a bailout loan to aid its struggling economy.
Another sticking point was the imprisonment of Yanukovych's main foe, former premier and Orange Revolution heroine Yulia Tymoshenko.
Protests continued overnight, with demonstrators camping out in tents on a central square.
Round-the-clock rallies are planned for the rest of the week in a bid to urge Yanukovych to change his mind and sign the agreement at a summit in Lithuania on Friday.
