Medvedev made the announcement as he began a two-day official visit to Beijing, Xinhua, the Chinese government news agency, reported. He said the oil agreement calls for an additional 10 million tons a year for 10 years.
After meeting with Chinese Prime Minister Li Keqiang, Medvedev said the relationship between China and Russia is as close as it has ever been.
"Bilateral relations have never reached such high levels. It is a good thing because we are neighbors," he said.
Medvedev said he expects trade between the two countries to increase from the record level of $88 billion in 2012.
The Soviet Union and China were close allies in the early years of Mao Zedong's rule. But the relationship quickly became strained, and there was open hostility, fed by border disputes, from 1960 to 1989, when the Soviet Union was disbanded.