The Obama administration is warning Russia that it could face additional sanctions if it fails to adhere to a new international deal on Ukraine or moves its forces on the border into eastern Ukraine.
President Barack Obama's national security advisor, Susan Rice, told reporters at the White House Friday that the U.S. has been clear that it and its European partners "remain ready to impose additional costs on Russia" if it fails to meet its obligations.
She said "in the event of a dramatic escalation," such as the movement of troops, those costs and sanctions could include targeting what she called "very significant sectors" of the Russian economy.
Rice reiterated an earlier statement by State Department spokeswoman Jen Psaki that the U.S. believes Russia has a responsibility to use its influence to restrain and withdraw the pro-Russian militants occupying government buildings in eastern Ukraine.
But pro-Russian militant leader Denis Pushilin in eastern Ukraine said earlier that his men are not bound by the deal and will only stand down after the Ukrainian government resigns.
Psaki said Friday the U.S. rejects those comments and the separatists' claim that the new Ukrainian government took power in a coup.
Thursday's agreement, which followed talks between Ukraine, Russia, the United States and the European Union, calls for all government buildings to be evacuated and for the militants to be disarmed.
But it includes few concrete measures for ending the crisis, and many Western leaders are skeptical about Russia holding up its end of the bargain.
Rice said the U.S. will see over the coming days whether Russia upholds its agreement, while Psaki told reporters the U.S. is "clear-eyed" about Russia's record of not implementing steps in the past.
The seven-paragraph agreement does not specifically require Moscow to withdraw 40,000 troops massed on its border with Ukraine, and does not reference Russia's annexation of Ukraine's Crimean peninsula last month. It also does not obligate Moscow to hold direct talks with the interim government in Kyiv.
But the four-party statement says monitors from the Organization for Security and Cooperation in Europe will immediately begin to put the de-escalation measures into place.
Russian Foreign Minister Sergei Lavrov spoke separately following the Geneva talks, saying the four parties will work to establish a broad national dialogue to ensure protection of Ukrainians' rights.
Moscow has repeatedly insisted it has the right to protect Russian speakers in Ukraine. It accuses the new Ukrainian leadership of being anti-Russian and anti-Semitic, and of threatening the rights of pro-Russians.
Pro-Russian gunmen have seized Ukrainian government buildings in nearly a dozen eastern towns and cities, while Ukrainian troops have launched operations to retake the buildings. It remains unclear how much actual fighting has taken place.