Kiev’s operations against pro-Russian militants in eastern Ukraine have been suspended over Easter, Foreign Minister Andriy Deshchytsia has announced.
However, Andriy Deshchytsia said, Ukraine’s security services would resume military action if the separatists continued to occupy government offices.
They are refusing to leave buildings in several cities, defying an agreement reached on Thursday to ease the crisis.
The US has threatened more sanctions if Russia fails to abide by the agreement.
The Kremlin responded by accusing the White House of treating Moscow like a “guilty schoolboy”.
In a separate development, Russian President Vladimir Putin said he would award medals to Russians who took part in the seizure of Crimea from Ukraine last month.
The Ukrainian foreign minister added that the Organization for Security and Cooperation in Europe (OSCE) was willing to start a negotiation process with the separatists.
In response to separatist calls for pro-European protesters in Kiev to also vacate sites they were occupying, he said that those camped in the capital’s Maidan Square had “asked permission from the city council” and their camp was therefore not an “illegal occupation”.
Russia, Ukraine, the EU and US had agreed during talks in Geneva that illegal military groups in Ukraine must be dissolved, and that those occupying government premises must be disarmed and leave.
The sides also decided there would be an amnesty for all anti-government protesters.
But the separatists’ spokesman in the city of Donetsk said that the Kiev government was “illegal”, and vowed they would not go until it stepped down.
After cautiously welcoming the deal struck on Thursday, the White House stepped up pressure on Russia to use its influence over separatists occupying the buildings in nine cities and towns in eastern Ukraine.
On Friday, US National Security Adviser Susan Rice warned that if Moscow failed to uphold the deal a new round of sanctions would focus on what she called “very significant sectors of the Russian economy”.
Susan Rice added that the US had identified close associates of the Russian leadership as potential targets for new sanctions.
Russia responded by saying it was disappointed with the US assessment of the Geneva deal.
“You can’t treat Russia like a guilty schoolboy who has to… show he has done his homework,” President Vladimir Putin’s spokesman, Dmitry Peskov, said.
“That kind of language is unacceptable.”