Tymoshenko stopped short of saying she would join Ukraine's official opposition, but said she and her supporters would form a "parallel" force to Yushchenko's backers to compete in the elections set for March 2006.
"I and Viktor Andriyovych [Yushchenko] will go to the elections in parallel ways,"Tymoshenko said. "It does not mean it is a war. There will be two different teams, with absolutely different people. I will not go to the elections with those people who have discredited Ukraine so much -- I do not mean the president, but his closest circle."
No reaction to Tymoshenko's comments was immediately available from Yushchenko.
Yushchenko says he is seeking to get a new government in place quickly under his ally Yuriy Yekhanurov, whom he has appointed acting prime minister.
Former Prime Minister Tymoshenko To Go It Alone
President Sacks Government, Offering More Questions Than Answers
RFE/RL Interviews Prime Minister Yuliya Tymoshenko