The United States says the deal between Ukraine's president and the opposition ending the country's political crisis is "very very fragile" and needs global support.
A State Department official said Friday that this will be a "tough sell" to the opposition in the streets because of the violence and deaths.
President Barack Obama telephoned Russian President Vladimir Putin Friday to talk about Ukraine. The official says both leaders agree on the need to quickly implement the deal and encourage all sides to avoid violence.
The official says Mr. Putin affirmed that Russia wants to be part of the implementation process. He also talked about the need to stabilize the Ukrainian economy.
A U.N. spokesperson says Secretary-General Ban Ki-moon phoned Ukrainian President Viktor Yanukovych to personally welcome the agreement. The official says Mr. Ban commends the spirit of compromise.
President Yanukovych and opposition leaders signed a deal Friday that returns the country back to the 2004 constitution, limiting presidential powers. The deal also includes setting up a coalition government and early elections.
Foreign ministers from France, Germany, and Poland helped broker the deal.
Protests erupted in Ukraine in November when President Yanukovych backed out of a trade deal with the European Union in favor of closer ties to Russia.
The protests began peacefully but sank into violence earlier this month, leaving about 100 people dead, including some protesters shot in the head by police snipers.
The deal would also replace Interior Minister Vitali Zakharchenko, who the opposition blames for the deaths of protesters. It amends the criminal code to allow for the release of release of former prime minister Yulia Tymoshenko from prison.
Ukraine is split among those in the east who favor ties with Russia, and those in the west who lean towards the European Union.
President Obama is downplaying suggestions that Ukraine is a battlefield in a new Cold War with Russia. He said this week that the U.S. wants to make sure the people of Ukraine are able to make their own decision about the future.
A State Department official says the U.S, Europe, Russia, and Ukraine all have shared interests.