In a letter to Ukrainian President Viktor Yushchenko released by the Kremlin on Friday, the Russian president accused Kiev of using the Stalin-era famine, known as the Holodomor, to drive a wedge between Ukraine and Russia, and urged efforts to forge a common position on the tragedy.
In the letter, Medvedev said Ukraine's attempts to declare the Holodomor an act of genocide by the Soviet authorities meant he could not attend commemoration events in Kiev.
"Of course, disappointment is felt in Kiev," Ambassador Konstyantyn Hryshchenko told the Ekho Moskvy radio station.
Eight heads of state, including the presidents of the Baltic States, Poland and Georgia, are expected to attend an international forum and commemoration events on the 75th anniversary of the Holodomor, which are taking place in the country's capital until Saturday. Some 40 foreign delegations are also expected to attend.
"Ukrainian politicians of different levels have repeatedly and consistently stated that they [events to mark the anniversary of the famine] are not about any responsibility or link with the modern Russia," Hryshchenko said. "It is about revealing historical facts and the responsibility of the Stalin regime."
The ambassador added that Ukraine would continue to raise the issue in international organizations.
Ukraine has been seeking international recognition for the Stalin-era famine as an act of genocide by the Soviet authorities following a similar move by Ukraine's Supreme Rada in late 2006. The United Nations General Committee refused last month to include the famine on its agenda, supporting Russia's recommendation to exclude the Holodomor from the UN session.
"We would like to draw attention to the greatest tragedy of the 20th century," the ambassador said. "Indeed, before Ukraine had raised the issue, no one spoke about it seriously, either in Russia or any other post-Soviet state."
Andriy Honcharuk, a deputy head of the Ukrainian presidential staff, also expressed regrets about Russia's refusal to participate in the events.
"We regret that our eastern neighbors, our partner Russia, will not take part in the events, but I think that time and history will judge this situation," Honcharuk told a briefing in Kiev.
Russia had previously accused the Ukrainian leadership of using the historical humanitarian tragedy for its own political ends, as well as to spread ethnic animosity and divert Ukrainians' attention from the ongoing political and economic crisis in the country.
The Russian Foreign Ministry said that besides Ukraine the famine affected different ethnic groups in vast territories - the North Caucasus, the Volga region, central Russia, Kazakhstan, west Siberia and the southern Urals.
Estimates vary widely as to the number of deaths in Ukraine caused by the forced collectivization of the early 1930s, along with the devastating purges of Ukrainian intelligentsia, religious leaders and politicians under Stalin. Some sources cite figures of over 7 million.
The European Parliament adopted a resolution in October declaring the famine of 1932-1933 a crime "against humanity" but stopping short of using the word "genocide." In July 2008, the Parliamentary Assembly of the Organization for Security and Cooperation in Europe also condemned the famine without recognizing it as an act of genocide.