MOSCOW (AP) -- Ukraine's president called Tuesday for new sanctions against Russia over its decision to recognize passports issued by separatist authorities in eastern Ukraine, while the Kremlin accused Ukraine of denying vital documents to people in the rebel regions.
The Kremlin said its decision is a "humanitarian" move to help residents of rebel-held areas in eastern Ukraine who are suffering from a blockade by Ukrainian nationalists, and says that doesn't amount to recognizing the rebel regions.
The United States rejected the move, calling the passports "illegitimate." In Washington, State Department spokesman Mark Toner said Russia's action "undermines efforts to bring peace to eastern Ukraine."
Ukrainian forces have been fighting Russia-backed separatists in eastern Ukraine since April 2014, a conflict that has killed more than 9,800 people. A 2015 agreement on resolving the conflict has been widely flouted by both sides.
As the war continues, a peace plan crafted by two associates of U.S. President Donald Trump and a Ukrainian parliament member caused a stir. The plan, which its proponents reportedly tried to peddle to the Trump administration, calls for measures including leasing Crimea to Russia.
Russia annexed Crimea in 2014 soon after Ukraine's Russia-friendly president fled the country in the wake of massive street protests.
Prosecutor-General Yuriy Lutsenko said Tuesday that an investigation would be opened against the parliament member, Andrei Artemenko, on possible treason charges.
Ukrainian President Petro Poroshenko on Tuesday denounced Moscow's documents recognition as contradicting the 2015 peace agreement. Speaking at a meeting with an EU aid commissioner, Poroshenko called for "resolute action, up to strengthening sanctions."
The United States and the European Union have both placed sanctions on Russia for its annexation of Crimea and its support for pro-Russian insurgents in eastern Ukraine.
The February 2015 peace agreement brokered by France and Germany has helped reduce fighting in eastern Ukraine, but clashes have continued and prospects for a political settlement have stalled.
Russian Foreign Minister Sergey Lavrov argued Tuesday that the decision to recognize passports and other documents issued by separatist authorities in the east was aimed to protect the rights of residents.
"The Ukrainian authorities are doing all they can to make life as difficult as possible for the residents of those territories and make it as hard as possible for them to enjoy the most basic rights and freedoms," Lavrov said. "It's hard and often impossible to exercise those rights without documents."
Jim Heintz in Moscow and Josh Lederman in Washington contributed to this story.