KIEV, Ukraine – Opposition leader Viktor Yushchenko praised thousands of his supporters last night, telling a roaring, orange-clad crowd that they changed the country without bloodshed – but he also warned of trouble during this weekend’s presidential runoff.

Mr. Yushchenko did not say who was plotting against Sunday’s court-ordered vote, but told supporters at a rally in Kiev that he was “calling on your courage to defend the results of the election.”

“The vote on December 26 will not be an easy political walk,” Mr. Yushchenko said in freezing temperatures on Independence Square to mark one month since the beginning of the “orange revolution” protests. “There are some forces preparing to disrupt and they are preparing brigades, groups who are readying to come to Kiev.”

“We will come on this square, this stage, after the vote on December 26, and will stay until our victory is celebrated,” he said.

The call echoed an appeal he made after the November 21 runoff that his rival Prime Minister Yanukovich won until the Supreme Court annulled the vote, citing fraud. It ordered a new vote for Sunday.

For nearly three weeks, Independence Square was the scene of protests that paralyzed the government in this former Soviet republic. Protesters set up a sprawling tent camp on the tree lined main street, bringing central Kiev to a halt.

Fears of violence have been high ahead of the new balloting, with rumors swirling that pro-Yanukovich supporters are being given weapons and poised to head to Kiev after the vote. Mr. Yanukovich’s campaign staff has repeatedly denied the allegations.

But Mr. Yanukovich has openly warned that even if Mr. Yushchenko wins the new runoff, he will never be considered president of all of Ukraine. The heated campaign has divided the country between the pro-Yanukovich industrial, Russian-speaking east, and the west and center where Mr. Yushchenko draws his support.

Some eastern regions have raised the possibility of pursuing autonomy if Mr. Yushchenko wins, but most of those plans appear to have dissipated in recent weeks.

“I would suggest that there is no ground to relax given…the clear statements by some regional authorities which support Mr. Yanukovich,” said a Kiev-based political analyst, Leonid Polyakov. “The issue of separatism, which potentially can include violence, could still remain on the agenda until the voting is finished.”

As Mr. Yushchenko spoke, the crowd, wearing orange armbands, waved orange banners and chanted his name. A stage with orange Christmas trees in the square was lit up, and the rap song that became synonymous with the earlier protests again blasted from giant loudspeakers. A 23-foot-high balloon resembling a giant orange was tethered to the ground on one side of the square.

“Those were really revolutionary days – so much work to change a hated regime has never been done before,” said Mr. Yushchenko, wearing a trademark orange scarf. “This history lesson will never be forgotten.”

Referring to the revote, Mr. Yushchenko said: “The doors have been opened. The only thing left for us is to step over the threshold.”

Mr. Yushchenko, relying on the protests and the outcry over the fraudulent vote, has found himself facing a weakened and increasingly isolated opponent. Mr. Yanukovich has been abandoned by outgoing President Kuchma and even appears to be losing the support of the Kremlin.

Mr. Yushchenko told the crowd that they changed Ukraine “peacefully, beautifully, elegantly, and without any drops of blood.”

“You should applaud yourselves because in this difficult period, we didn’t stay in our apartments…but came to the square,” he said.

Bundled in a fur hat and coat, Lyudmila Kashchenko, 45, said: “I am tired of the revolution, but I am more tired of our authorities.”

Earlier yesterday, Mr. Yushchenko pledged to make Moscow his first official destination if he is elected, a statement that came a day after President Putin promised to work with the new president.

But Mr. Yushchenko also insisted that attempts to make Russian the country’s second official language had become a political issue and required extensive discussion.

The language issue has become key. Almost 70% of the population uses Russian on a daily basis, but Ukrainian predominates in the more nationalistic west.

Mr. Yanukovich wants Russian given official status alongside Ukrainian, which is constitutionally protected as the language of government, the police and military, universities, and most schools.