BRUSSELS, Sept. 11 - European Union governments agreed on Thursday to begin their new sanctions against Russia over the Ukraine crisis on Friday but could lift them next month if Moscow abides by a fragile truce, while the United States prepared its own fresh sanctions, Reuters reported.

The steps are the latest by the United States and the EU following Russia's annexation of Crimea in March and what the West sees as an effort since then to further destabilize Ukraine by backing pro-Russian separatists with troops and arms.

President Barack Obama said he will provide details on the new U.S. sanctions on Friday. The United States plans to sanction Sberbank, Russia's largest bank, and to further limit other Russian banks' access to U.S. capital, sources familiar with the matter said on Thursday.

The 28 governments of EU member states last week agreed on the new sanctions against Russia but spent several days wrangling over their announcement and implementation.

Russia's foreign ministry said the approval of the new EU penalties showed the European Union had "made its choice against" the current peace road map aimed at ending the worst confrontation between Moscow and the West since the Cold War.

After EU ambassadors gave the go-ahead to the new sanctions to go into effect on Friday, European Council President Herman Van Rompuy said EU officials would conduct a review before the end of September of how the truce reached last week between Ukraine government forces and rebels was working. If Russia was complying, some or all sanctions could be lifted, he said.

"If the situation on the ground so warrants," he said, officials may submit to EU leaders "proposals to amend, suspend or repeal the set of sanctions in force, in all or in part".

That enticement to Moscow to cooperate, while immediately imposing new measures, reflects impatience on the part of some leaders not to pull punches after less than a week of the truce but also concern among others, especially those most heavily dependent on Russian trade, not to provoke Moscow's retaliation.

The EU agreement on the timing of the sanctions followed a phone call on Thursday involving Van Rompuy, British Prime Minister David Cameron, German Chancellor Angela Merkel, French President Francois Hollande and Italian Prime Minister Matteo Renzi, Cameron's spokesman said in London.

"If Russia genuinely reverses course, then of course the European Union and others will return to the subject, but there unfortunately has been very little evidence so far and that is why you have the European Union going ahead," the spokesman said.

Western powers have accused Russia of sending tanks and troops into eastern Ukraine to prop up a rebellion by pro-Moscow separatists. The Kremlin denies that and has responded with its own sanctions and threats of more retaliation. (rt/ez)