WASHINGTON, Feb. 21 -- U.S. President Barack Obama and his Russian counterpart Vladimir Putin agreed Friday on the need to quickly implement an agreement aimed at ending the Ukraine crisis.

Both leaders stressed the importance of stabilizing Ukraine's economic situation and undertaking necessary reforms, as they exchanged views on a range of global issues via phone, the White House said in a statement.

Obama and Putin also agreed on the need for all sides in Ukraine's current political crisis to refrain from further violence, it added.

Ukrainian President Viktor Yanukovych and the opposition signed the agreement Friday in a bid to end the country's political crisis which has left dozens of people dead and hundreds of others injured.

The accord envisages constitutional changes that would limit presidential power, and holding early presidential elections this year instead of March 2015, and a formation of a national unity government within 10 days.

In a separate statement issued earlier Friday, the White House said it welcomes the deal and calls for immediate implementation of the initial steps, which include an end to the violence, amnesty and security normalization, and passage of the constitutional package in the parliament.

White House spokesman Jay Carney told the daily press briefing Friday that signing of the deal doesn't necessarily mean the United States would not impose additional sanctions on Ukraine.

In their telephone conversation, Obama and Putin also spoke about the importance of efforts to achieve a political solution in Syria and the need for the Syrian government to adhere to its commitment to eliminate its chemical weapons program, according to the statement.

In addition, they discussed cooperation on the ongoing talks on Iran's nuclear program, said the statement, adding that Obama also congratulated Russia on its hosting of the Olympic games.

On Friday afternoon, U.S. Secretary of Defense Chuck Hagel and his Ukrainian counterpart Pavlo Lebedev had a phone conversation, during which Lebedev assured Hagel that the Ukrainian armed forces remain the protectors of the Ukrainian people and would not use arms against them.

According to the Pentagon, Hagel commended the Ukrainian government's decision to keep the military on the sidelines of the crisis thus far and urged continued restraint.