Pro-Russian separatists in eastern Ukraine agreed Monday to a four-day cease-fire and to further negotiations with the government, a move that could help quell a conflict that has paralyzed the nation and defer further E.U. and U.S. sanctions against Russia.

After the first official meeting between delegates from both sides, Alexander Borodai, the leader of the self-proclaimed Donetsk People’s Republic, said separatist fighters would honor the truce declared last week by Ukrainian President Petro Poroshenko and suspend hostilities until Friday. He also pledged to continue the talks.

Meanwhile, European Union foreign ministers met in Luxembourg to discuss imposing additional sanctions on Russia as early as Friday if the Ukraine situation does not de-escalate and as a similar U.S. sanctions deadline of early July approaches. President Obama and Russian President Vladimir Putin spoke Monday about the conflict, the White House said.

The Ukrainian National Security and Defense Council said Monday that things had quieted during the day after shelling from pro-Russian forces over the weekend. But in a conflict in which separatists have often fought among themselves, it was not clear whether the cease-fire would be observed by all those who have taken up arms against the government and seized control of administrative buildings and territory in the east.

The meeting Monday in the regional capital of Donetsk was attended by Donetsk separatist leaders, the head of the Ukraine mission of the Organization for Security and Cooperation in Europe, Russia’s ambassador to Ukraine and former Ukrainian president Leonid Kuchma, among others. Poroshenko sent Kuchma, a conciliatory figure from eastern Ukraine who was president from 1994 to 2005, as his representative.

“Both sides will respect this, God willing,” Kuchma told reporters in Donetsk after the meeting, saying that he hoped to get a peace process on track during the break in hostilities.

The separatist conflict began after the ouster in February of Russia-friendly President Viktor Yanukovych and Russia’s subsequent annexation of the Crimean Peninsula. Kiev’s control of the east has slipped steadily since then, and Russian volunteer fighters have easily been able to flow over the border into Ukraine.

Last week, Poroshenko announced the cease-fire and offered a peace plan that he said would give more power to Ukraine’s regions, a key demand of the industrial heartland in the east. But until Monday it was unclear whether he would be willing to sit down with separatist leaders, whom he has described as terrorists.

Even as the talks were being held, Ukrainian law enforcement officials issued arrest warrants for some of the leaders, including Borodai.

“In response to the cease-fire by Kiev, we pledge to stop fighting on our part,” Borodai, a Russian citizen, said on Rossiya 24 television after the meeting. “We hope that through the period of cease-fire on both sides, we will manage to come to terms and start consultations on how talks will proceed on the peaceful settlement of the conflict.”

Another separatist leader suggested holding the next round of talks in Slovyansk, a rebel-held city that is encircled by government forces and has been the scene of some of the worst violence.

Russia has sent mixed signals about whether it supports Poroshenko’s efforts, with Foreign Minister Sergei Lavrov initially dismissing the cease-fire but Putin sounding more positive about it on Sunday.

In a possible sign of increased Kremlin efforts to exert control over the separatists, Putin offered a close friend, pro-Russian Ukrainian politician Viktor Medvedchuk, as an interlocutor on their behalf. Medvedchuk — who has said that Putin is the godfather to one of his children — was at the table Monday.

Putin and Obama had a “detailed discussion” Monday about the conflict in Ukraine, the Kremlin said. “Vladimir Putin stressed that the cessation of hostilities and direct negotiations between the parties to the conflict would be of priority significance for the normalization of the situation in the southeastern regions,” it said.