Miss Tymoshenko has revealed that she has been summoned by prosecutors to answer the president's charge of treason as Ukraine's two rulers battle it out for power ahead of a 2010 presidential vote over their country's future direction.
President Yushchenko has accused the prime minister of failing to condemn Russia's actions in Georgia, and the presence of the Russian naval fleet in Ukraine, in exchange for political support from the Kremlin.
Miss Tymoshenko hotly denies the allegations. The Ukraine's prosecutor has declined to comment.
Mr Yushchenko and Miss Tymoshenko both led the popular 2004 Orange Revolution against the electoral corruption and intimidation of Ukraine's old regime but the pair's troubled governing coalition collapsed five days ago over the question of Russia and Georgia.
Under the constitution, a new Ukrainian government must be formed over the next week otherwise Mr Yushchenko, who precipitated the coalition's collapse, has threatened to dissolve the country's parliament and call new national elections.
"The president used the Georgian issue against me as a rival in the presidential candidate in 2010," said Miss Tymoshenko.
"I would have supported Yushchenko for the second term in the president's office had he not ruined the democratic coalition."
Mr Yushchenko, who is pro-West, will represent the Ukraine at a meeting with the European Union in the French town of Evian of Tuesday.
The EU is expected to offer Ukraine encouragement, closer ties and the prospect of a relaxed visa regime, but will stop short an explicit pledge on future membership.
A draft document acknowledges Ukraine's European aspirations and added "gradual convergence of Ukraine with the EU in political, economic and legal areas will contribute to further progress in EU-Ukraine relations".
Russia has expressed opposition to EU and Nato membership for Ukraine, a former Soviet state, a stance that has echoed Moscow's position in the run-up to this summer's Russian military intervention in Georgia.
EU countries, such as Germany or Italy, are cautious of antagonising Russia over the issue of Ukraine's membership, the country is a key transition route for vital gas supplies to Europe and previous disputes between Kiev and Moscow have led to European energy shortages.
Other countries, such as Britain, back a strong EU message to Moscow on Ukraine's future as a European member state.
David Miliband, the Foreign Secretary, has warned that the political upheaval in Ukraine should not lead to national disunity in the face of Russia.
"Equally, it is important that Europe's leaders make clear that we are determined on a long-term relationship with Ukraine with membership as a long-term goal," he said on Sunday.
A senior United States official predicted on Monday that both Ukraine and Georgia will be offered eventual Nato membership, a move that means the western alliance would be committed to war should either country be attacked by Russia in the future.