U.S. Vice President Joe Biden spoke with Ukrainian President Petro Poroshenko by phone Saturday to discuss U.S. military aid to Ukrainian fighters and to call on Russian-backed fighters to adhere to a ceasefire agreement, according to U.S. and Ukrainian government statements. Both leaders urged Russia and separatists in eastern Ukraine to abide by the terms of the Minsk agreements adopted in September and February, the White House said in a statement. The agreement, brokered by German Chancellor Angela Merkel and French President Francois Hollande, calls for withdrawal of heavy artillery from war zones, a prisoner exchange and full access to the conflict site by monitors of the Organization for Security and Cooperation of Europe.

The Ukrainian government also said the leaders discussed U.S. aid to Ukraine, “both financial and in the sphere of military-technical cooperation,” Sputnik news agency reported.

The Obama administration Wednesday announced a fresh round of sanctions on pro-Russian rebels, and said it was sending an additional $75 million to Ukraine in non-lethal military aid.

Neither statement mentioned whether Biden and Poroshenko discussed U.S. weapons for Ukrainian forces, a topic that has been the subject of international debate in recent months. President Obama reportedly agreed to hold off on sending lethal arms to Ukraine for the moment to allow a diplomatic solution to take hold, Peter Wittig, the German ambassador to the U.S., told the Associated Press.

Meanwhile, Poroshenko said Ukraine had contracts with several European countries for supplies, including lethal weapons, after the EU lifted its embargo on arms shipments , the Russian news service Interfax reported on its Ukraine service. “If a new wave of aggression begins against Ukraine, I can state with confidence that we will immediately get both lethal weapons and a new wave of sanctions against the aggressor,” he said in a television interview.

Poroshenko didn’t detail which EU countries had such contracts, but Poland reportedly began discussions with Ukraine on possibly sending weapons. Poland has purchased U.S. weapons, opening up the possibility that U.S.-made lethal weapons could be included in shipments to Ukraine if the two countries decide to go ahead with such a plan. But the Polish government has emphasized no decision has yet been made on that front.