A Ukrainian soldier walks at a checkpoint near Slaviansk in eastern Ukraine July 3, 2014. About half the 130,000 residents of Slaviansk are thought to have fled since fighters who want eastern Ukraine incorporated into Russia took control of the city in April, a month after Moscow annexed the Black Sea peninsula of Crimea. Since then, government forces trying to end the rebellion in towns and cities across the Russian-speaking region have pounded separatist positions in and around Slaviansk. Picture taken July 3, 2014. REUTERS/Andrew Kravchenko/Pool

Just days after calling off a 10-day cease-fire with eastern Ukrainian separatists, Ukrainian President Petro Poroshenko said he’s offered a time and place on Saturday to resume peace talks with separatists.

The proposal comes as 13 Ukrainian servicemen were killed in fighting on Friday alone.

Earlier this week, the foreign ministers of Ukraine, Russia, France and Germany met in Berlin and agreed to talks between themselves and eastern separatists no later than Saturday “with the goal of reaching an unconditional and mutually agreed sustainable cease-fire.”

The Organization for Security and Cooperation in Europe (OSCE) will mediate if separatists agree to the talks. Russia agreed to allow OSCE observers and Ukrainian troops to monitor the Russian-Ukrainian border, which was one of Ukrainian Foreign Minister Pavlo Klimkin’s requests during the Berlin talks. Ukrainian and Western officials have accused Russia of sending weapons across the border to separatists. Klimkin also wants all hostages in the east to be released.

Russian Foreign Minister Sergey Lavrov suggested the “contact group” meet in a “safe territory” in Ukraine and criticized Kiev’s unilateral cease-fire and declarations, arguing that “none will lay down arms unilaterally.”

The contact group is made up of Poroshenko, the Russian ambassador to Ukraine, an OSCE official, and now would include a representative of the eastern separatists. A Western diplomat says talks could happen in Donetsk, an epicenter of separatism in the east, according to Reuters.

18 Ukrainian servicemen have been killed since Poroshenko halted the cease-fire on Monday. Poroshenko vowed to go on the attack and “liberate our land” in his address that ended the cease-fire. Poroshenko argued he was ending the cease-fire because separatists did not respect it. The Ukrainian military has since undertaken 100 or so operations in the east. There are no figures for how many separatists or civilians have been killed since the cease-fire ended.

The OSCE reports the mood in the east is still tense, and three policemen in Donetsk were killed on Friday. Russia state-owned television said a Russian news cameraman was killed by Ukrainian servicemen during clashes with the separatists he was covering.