MOSCOW (Sputnik) - Former UK Prime Minister Boris Johnson has revealed details of his phone conversation with Russian President Vladimir Putin that took place just before the start of Russia’s special military operation in Ukraine, UK media reports.

Johnson warned the Russian president that there would be tougher Western sanctions and that support for NATO would increase if Russia were to start military action.

Johnson’s comments will air later on Monday as part of a three-part documentary for UK media.

Russian Deputy Foreign Minister Sergey Ryabkov told Sputnik that Russia had repeatedly warned NATO that there would be consequences for the alliance’s attempts to expand eastward.

In December, Russian Defense Minister Sergei Shoigu said that the emphasis in the activities of the operational and combat training of the Russian army in 2023 would be placed on the threats associated with the expansion of NATO to the East.

Russia launched its special military operation in Ukraine on February 24, 2022, after the Donetsk and Lugansk people’s republics appealed for help in defending themselves against Ukrainian provocations. In response to Russia’s operation, Western countries have rolled out a comprehensive sanctions campaign against Moscow and have been supplying weapons to Ukraine.

Moscow has always described NATO as an alliance aimed at confrontation. Kremlin spokesman Dmitry Peskov said in early April, 2022, that the alliance's further expansion toward Russian borders was aggressive in nature and would not make Europe more secure.

At the start of January, Peskov said that the EU and NATO have supplied "tens of billions of dollars" worth of arms to Ukraine.