WASHINGTON — Two days before he fled Ukraine’s capital, President Viktor Yanukovych huddled on the phone for more than an hour with Vice President Joe Biden, his primary conduit with the U.S. government throughout the political crisis consuming the former Soviet republic.

The window for a resolution to the crisis was closing quickly ”“ and may already have closed, Biden warned Yanukovych, according to a senior administration official familiar with the conversation. Yanukovych was initially defiant, the official said, and accused the protesters in the streets of Kiev of being terrorists. Though Yanukovych became less resistant to Biden’s appeals as the call continued, the vice president hung up the phone uncertain of the embattled leader’s next move.

What followed was a rapid series of developments that left Yanukovych’s fate ”“ and the broader political situation in Ukraine ”“ highly uncertain. On Friday, Yanukovych agreed to form a new government and hold an early election. Ukraine’s parliament slashed the president’s powers and voted to free his rival, former Prime Minister Yulia Tymoshenko, from prison. And on Saturday, Yanukovych fled Kiev, reportedly holing up in Crimea, a pro-Russian area of Ukraine.

The tenuous political agreement was orchestrated by European diplomats, with the U.S. and Russia playing supporting roles.

Biden, who had built a working relationship with Yanukovych since becoming vice president, was at the forefront of the delicate diplomatic maneuvering for the Obama administration. He spoke to Yanukovych on the phone nine times during the three-month political crisis, an unusual level of contact that underscored the heightened U.S. concern about stability in Ukraine, a strategically located nation that shares a border with Russia.

The vice president also met throughout the crisis with Ukrainian religious leaders and Ukrainian-American groups, according to the administration official, who was not authorized to discuss the vice president’s involvement by name and insisted on anonymity.

Biden’s prominent role in the diplomatic wrangling comes at a time when his foreign policy credentials have been called into question by former Defense Secretary Robert Gates, who wrote in a recent memoir that the vice president has been “wrong on nearly every major foreign policy and national security issue over the past four decades.” Gates’ criticism, coming as Biden contemplates a presidential run in 2016, was a sharp blow to the vice president, for years the chairman of the Senate Foreign Relations Committee when he represented Delaware in the Senate.

Biden and Yanukovych first met in 2009 when the newly sworn-in American vice president traveled to Ukraine. Yanukovych was an opposition political leader with an eye on the presidency. Ukraine’s conflicted loyalties between Europe and Russia, which are at the center of the current crisis, were already bubbling to the surface during that visit.

“We do not recognize ”“ and I want to reiterate it ”“ any sphere of influence,” Biden said during his 2009 visit to Kiev. “We do not recognize anyone else’s right to dictate to you or any other country what alliances you will seek to belong to or what bilateral relationships you have.”

Ukraine was moving to deepen its ties to Europe when Yanukovych announced this past November that he was abandoning an agreement with the European Union and instead was seeking closer cooperation with Moscow. Protesters took to the streets, seizing control of Kiev City Hall and coming under brutal attack by police. Dozens of people were killed in clashes last week.

As the protests grew, Biden warned Yanukovych that he had seen similar situations play out before around the world. The vice president, speaking to Yanukovych through a translator from his office in the West Wing, used an American expression to make his point, telling the Ukrainian that leaders are often “a day late and a dollar short” with their attempts to appease political protesters.

Yanukovych often seemed torn between the choices before him and rarely gave Biden a clear signal of his next move, the official said. Biden and Yanukovych have not spoken since the Ukrainian leader fled Kiev over the weekend.

Yanukovych’s hasty retreat from the capital has left the Ukrainian parliament speaker nominally in charge of the country, though Russian officials say they question the legitimacy of the acting government, raising concerns about the fragile state of the current agreement.

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