MOSCOW — Russian President Dmitri A. Medvedev on Monday ordered Gazprom to cut deliveries of natural gas deliveries to Belarus over unpaid debts, a step which could jeopardize supplies to Poland and other European countries.

At a morning meeting with Mr. Medvedev, Aleksei Miller, the chief executive of Gazprom, said Belarus was willing to pay its debts through barter, and Mr. Medvedev tartly refused such an arrangement, saying, “Gazprom cannot accept payment for debt in pies, butter, cheese or other means of payment.”

He then ordered Gazprom to gradually reduce supplies sent through Belarus, whose pipelines carry roughly 20 percent of Russia’s natural gas to Europe.

President Aleksandr G.. Lukashenko has said Belarus has no debts to Gazprom, and one of his top officials complained this weekend about Russia’s strong-arm pricing policies.

“It would be good if our Russian partners realized that their relationships within the CIS do not have to be based on Russian terms,” said Deputy Prime Minister Andrei Kobyakov, who was in St. Petersburg for the International Economic Forum.

Mr. Medvedev’s decision comes in a tendentious political context, as Mr. Lukashenko, once the Kremlin’s staunchest regional allies, hangs back from key Russian initiatives. Over the last two years, Mr. Lukashenko has pursued partnerships with the West, agreeing to join the European Union’s Eastern Partnership.

Belarus has refused to sign off on the creation of a customs union with Russia and Kazakhstan unless Russia lifts customs duties on oil to Belarus. It has also offered a safe haven to the former president of Kyrgyzstan, Kurmanbek S. Bakiyev, who was forced from office this spring by a popular uprising supported in part by Russian soft-power tactics. Belarus is the only member of the Collective Security Treaty Organization, a regional security group dominated by Russia, which has refused to sign off on stabilization measures for Kyrgyzstan.

Russian Foreign Minister Sergey V. Lavrov arrived in Minsk, the capital of Belarus, on Monday for two days of bilateral talks. A Foreign Ministry spokesman said Mr. Lavrov may have a personal meeting with Mr. Lukashenko.

Russia rushed to reassure Europe that its supplies would not be affected, saying consumption is low and Gazprom may be able to transport natural gas to Poland through Ukraine. Russia’s previous pricing dispute with Ukraine, which transports 80 percent of Russian gas exports to the west, threw Europe into crisis, something Moscow would be loath to repeat during a season when it is taking pain to repair its relationships with European capitals.