Ukraine's sacked Prime Minister, Yulia Tymoshenko, has bitterly attacked the dismissal of her government.
Yulia Tymoshenko helped secure Mr Yushchenko's victory
She blamed aides to President Viktor Yushchenko for the "deeply unjust" move on Thursday, saying they had schemed against her.
She had roused the crowds during the Orange Revolution which swept Mr Yushchenko into power last December.
But on Friday Ms Tymoshenko distanced herself from Mr Yushchenko, who has pledged to root out corruption.
"Today we are two different teams," she said. "I think these two teams will go their own way.
"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," she said.
However, she criticised Mr Yushchenko, saying he had "practically ruined our unity, our future, the future of the country," and added: "I think this step is absolutely illogical."
Ukraine's acting Prime Minister, Yuri Yekhanurov, has begun trying to form a new government.
Yuri Yekhanurov (right) was formerly a regional governor
President Yushchenko said he had sacked the government because it had become consumed by a power struggle.
He said he acted to preserve the ideals of the Orange Revolution, after his government had been accused of corruption.
Mr Yekhanurov said his priority would be to ensure stability.
Some of the old team are expected to be given jobs in the new administration, says the BBC's Helen Fawkes in Kiev.
The Orange Revolution ousted the regime of former President Leonid Kuchma, widely condemned as corrupt.
But the past week saw three senior government officials resign, precipitating Mr Yushchenko's dismissal of the government.
One of them, a presidential aide, alleged that corruption was worse now than under the previous authorities.
Mr Yushchenko said in-fighting between members of the team had affected affairs of state.
Correspondents say Ms Tymoshenko and the head of the Security and Defence Council, Petro Poroshenko, were at loggerheads from the start.
In a live interview on Ukrainian television, Ms Tymoshenko rejected claims that she had reneged on earlier commitments. She said her cabinet had done an extraordinary job and left the economy in good shape.