"When it comes to the discount, it is provided by the Russian government. This is our good will," Medvedev said at a meeting with Alexei Miller, head of Russian gas giant Gazprom.
The prime minister said he would sign the deal when all interested parties finalize their discussion of the issue.
Meanwhile, he demanded that Gazprom negotiate in line with the existing agreements. "All other talks (about new deals) are groundless," he said.
Under the current "winter package," which will expire on March 31, Kiev pays Russia 329 U.S. dollars per 1,000 cubic meters in the first quarter of 2015, which is 100 dollars below the market price.
The deal was reached between the two sides last October in Brussels under the mediation of the European Union.
Ukrainian Prime Minister Arseny Yatsenyuk announced earlier that Kiev planned to discuss a "summer package" of natural gas supplies with Russia and the EU on Friday this week.