MOSCOW -- A day after Russian leader Vladimir Putin proposed to President Barack Obama that they boost attempts to resolve their standoff over Ukraine peacefully, Secretary of State John Kerry scrambled his travel plans to meet with his Russian counterpart in Paris today, according to a U.S. State Department official and Russian news reports.
As the international tug-of-war over Ukraine's future continued, one of the best-known faces of the country's anti-government protests that set off the political crisis put aside his presidential ambitions and threw his support to a competitor in hopes of unifying forces behind a single, pro-Western candidate.
The announcement by Vitali Klitschko, a former world champion boxer, that he would back the billionaire chocolate magnate Petro Olekseyevich Poroshenko upended the race for president ahead of elections in May.
"The presidential elections in Ukraine on May 25 should join society and not become another war of everyone against everyone," Mr. Klitschko said at a meeting of his political party, the United Democratic Alliance for Reform. "This can be achieved only if you do not split the votes between the democratic candidates."
The months of demonstrations and political turmoil, which eventually toppled then-president, Viktor Yanukovych, centered on whether Kiev would tilt more toward Moscow or the West.
On Saturday, in an apparent bid to defuse tensions with the West, the Russian foreign minister, Sergey V. Lavrov, said in a television interview that Russia had "no intention" of invading Ukraine. Russia's recent rapid annexation of Crimea, combined with reports from the United States and NATO that it was massing troops along the Ukrainian border, had amplified fears that it planned to seize more Ukrainian territory.
Mr. Lavrov and Mr. Kerry spoke by telephone Saturday after Mr. Obama and Mr. Putin had agreed on fresh diplomacy.
After the phone call, Mr. Kerry delayed his return to the United States and headed for Paris to meet Mr. Lavrov today. He had been due back in Europe on Tuesday for a meeting of NATO foreign ministers.
"We are bringing our approaches closer together," Mr. Lavrov said in an interview on Russia 1 television, according to a transcript on the station's website. "My latest meeting with John Kerry in The Hague and my contacts with Germany, France and some other countries show that the possibility of a joint initiative is taking shape, which could be proposed to our Ukrainian colleagues."
There was no immediate U.S. response to his comments, but one administration official on Saturday cautioned that it is unlikely that a deal is imminent and noted the difference in tone between the statements issued by the United States and by Russia on what was said in the telephone call between the two presidents.
Russia's solution emphasizes a federation -- allowing for greater autonomy for eastern and southern Ukraine, with its heavy concentration of ethnic Russians. The stress Moscow puts a federation is seen partly as an attempt to ensure that Ukraine does not coalesce into a strong pro-European, anti-Russian country right next door.
Mr. Lavrov rejected as "absolutely unacceptable" the formula devised by Western officials, whereby Russia and Ukraine would negotiate directly with each other under Western auspices. The Russians reject the current leadership in Kiev as illegitimate. Mr. Lavrov repeated that the West should do more to curb the "lawlessness," in Ukraine, a formulation often interpreted as a veiled warning that Russia might intervene if the West and its allies do not push the Ukrainian leadership to bring stability.
But in his interview the Russian foreign minister stressed that Moscow was not contemplating an invasion.
The move by Mr. Klitschko on Saturday could propel Mr. Poroshenko to a formidable lead in the election, where his most prominent anticipated contender Yulia V. Tymoshenko, the country's former prime minister and a familiar if controversial figure in the country's tumultuous opposition movement. But it might also help Ms. Tymoshenko by removing one popular rival.
Mr. Klitschko said he would run instead for mayor of Kiev with a goal of transforming the city into a "truly European capital."
On Saturday, Mr. Poroshenko hailed the decision by Mr. Klitschko to step aside, saying it would serve the goals of the thousands of people who demonstrated for more than three months in hopes of putting Ukraine on the path to a pro-Western political future.
"It would be a betrayal if we did not unite," Mr. Poroshenko said in a speech to the United Democratic Alliance for Reform congress Saturday.
Mr. Poroshenko said that it was clear in light of the popular uprising, and the deaths of more than 80 demonstrators in clashes with the police before Mr. Yanukovych's ouster, that officials had an obligation to be more responsive to the public.
"Up until now in Ukrainian politics there has not been a case when two candidates for president who have the highest levels of support could take the step to unite," he added.
An aide said that Mr. Poroshenko would file paperwork to become an official candidate by Saturday evening.
On Thursday, Ms. Tymoshenko announced that she would run for president as the candidate of the Fatherland party. Mr. Tymoshenko, Mr. Yanukovych's archrival, spent 2 1/2 years in prison on charges that her supporters and the West have long criticized as politically motivated. Mr. Yanukovych narrowly defeated her in Ukraine's 2010 presidential election.
A spokesman for Ms. Tymoshenko, who was attending her own party congress Saturday, did not have an immediate response to Mr. Klitschko's announcement.
Ms. Tymoshenko is by the far the best-known politician in the race and an extremely charismatic speaker. But she faces an uphill climb, given the public's deep mistrust of anyone so closely associated with previous governments in a country with a long history of corruption and mismanagement.