WASHINGTON — The Obama administration signaled Monday it no longer recognizes Viktor Yanukovych as Ukraine’s president. The shift of support for opposition leaders in Kiev came even as U.S. officials sought to assure Russia that it does not have to be shut out of a future relationship with a new Ukrainian government.

Yanukovych was widely seen as a puppet of Moscow against Ukraine protesters who demanded stronger ties with the European Union to boost the faltering economy of the onetime Soviet state. His whereabouts were unknown after he fled the capital Kiev in the wake of deadly protests seeking his ouster.

U.S. officials said the International Monetary Fund was considering an aid package as high as $15 billion to help stabilize a new, transitional government in Kiev. White House spokesman Jay Carney said the U.S. would provide additional aid to complement the IMF, aimed at fostering Ukrainian economic stability, but it was not immediately clear how much money it would provide. Officials later said any U.S. assistance would seek to help Ukraine through political reforms, in part though investing more in health and education.

“Yanukovych left Kiev. He took his furniture, packed his bags, and we don’t have more information on his whereabouts,” State Department spokeswoman Jen Psaki told reporters. “So there are officials who have stepped in and are acting in response to that leadership gap at the moment.”

Carney said that although Yanukovych “was a democratically elected leader, his actions have undermined his legitimacy, and he is not actively leading the country at present.”

Senior U.S. officials, including Deputy Secretary of State William Burns and Treasury Secretary Jack Lew, are scheduled to meet with political, business and civil society leaders during a series of meetings in Kiev over the next two days. Top European Union officials are already there.

Psaki said Congress must approve any U.S. aid package, and several lawmakers on Monday called for a quick show of support for Ukraine’s new leaders.

“Now more than ever, the Ukrainian people need the continued support of their friends,” Sen. John McCain, R-Ariz., said in a statement. “The path of reform will be difficult, but if the new Ukrainian government is prepared to make these tough — and, at times, unpopular — decisions, it will need significant assistance from the IMF and the European Union. The United States must be ready to provide additional assistance as well.”

The protests in Kiev were sparked by Yanukovych’s shelving of an agreement with the European Union in November and turning instead for a $15 billion bailout loan from Russia. Within weeks, the protests expanded amid outrage over corruption and human rights abuses, leading to calls for Yanukovych’s resignation. Anger boiled over last week after 82 people, primarily demonstrators, were killed in clashes with security forces in the bloodiest violence in Ukraine’s post-Soviet history.

Aides said U.S. Vice President Joe Biden spoke Monday with Georgian Prime Minister Irakli Garibashvili in his first of several discussions about regional security, including with leaders of other former Soviet states who also are struggling, either politically or economically, against generations of inherent Russian influence. But Psaki said the emergence of a new government is Kiev is not “a zero-sum game for Russia or any other country.”

“It’s in all of our interests to support a prosperous future for the country,” said Psaki, underscoring the administration’s intent to acknowledge Ukraine’s desire to seek European aid and partnerships while still, perhaps, maintaining a productive relationship with Moscow.

But skepticism remains, including on Capitol Hill. Rep. Adam Schiff, D-Calif., urged Russia to refrain from interfering in Ukraine’s transition, noting that the new government in Kiev will “face a months-long process” of reorganizing and regaining the public trust.

“Any meddling or economic extortion will not put Russia’s chosen leader back in power or end the protests