“I don’t know Russia’s intentions,” Mr. Deshchytsia said, noting that during the negotiations, Russia’s foreign minister, Sergey V. Lavrov, had repeatedly asserted “that Russia was not involved.” He said Mr. Lavrov had been “cooperative and aggressive at the same time.”

Russia’s denials have stirred concerns that it went along with the agreement not to curb the turmoil in eastern Ukraine, but to blunt American and European calls for tougher sanctions that could severely damage Russia’s already sickly economy. Western sanctions have so far been limited to a travel ban and asset freeze on a few dozen individuals and a Russian bank.

Secretary of State John Kerry called Mr. Lavrov on Friday and urged Russia to ensure “full and immediate compliance” with the agreement, a senior State Department official said. Mr. Kerry, the official added, “made clear that the next few days would be a pivotal period for all sides to implement the statement’s provisions, particularly that all illegal armed groups must be disarmed and all illegally seized buildings must be returned to legitimate owners.”

Mr. Kerry also spoke with Ukraine’s acting prime minister and praised him for moving to carry out the deal, including by increasing transparency and guaranteeing amnesty for militants who disarm and leave occupied buildings. In Washington on Friday, Susan E. Rice, President Obama’s national security adviser, denounced anti-Semitic fliers distributed in Donetsk, which instructed Jewish residents to register, as “utterly sickening” and said Mr. Obama had “expressed his disgust quite bluntly.”

“They have no place in the 21st century,” she said.

American officials gave no firm timeline for when they expect militants to pull back, but said it should be days, not weeks. Vice President Joseph R. Biden Jr. is scheduled to travel to Ukraine on Tuesday, which could be a moment to assess whether the agreement has yielded results.

Russia responded with fury on Friday to remarks the day before by Mr. Obama, who said that the deal offered a “glimmer of hope” but that the United States would take more punitive action if Russia did not abide by it. The Foreign Ministry criticized Washington for making “ultimatums” and for moving “to threaten us with new sanctions, which is absolutely unacceptable.”

The diplomatic accord, while limited in scope and skirting the contentious issue of the Crimean Peninsula, was the first time Russia and Ukraine had found common ground since protests toppled a pro-Moscow government in Kiev in February, leading the Kremlin to seize Crimea and mass about 40,000 troops on Ukraine’s eastern border.