MOSCOW (Reuters) -The Kremlin warned on Monday that any expansion of NATO military infrastructure in Ukraine would cross one of President Vladimir Putin’s “red lines”, and Belarus said it had agreed to take action with Moscow to counter growing NATO activity.

The close ally of Moscow, Alexander Lukasenko from Belarus, has accused the United States for setting up training centers in Ukraine that he called military bases. According to him, he discussed the matter with Putin.

According to the RIA news agency, Lukashenko stated that “It is clear we must react to this …(We (all agreed) that we have to take some type of steps in response.”

Last week Ukraine started joint military exercises and was joined by other NATO members troops. Meanwhile, Russia and Belarus conducted large-scale drills which alarmed the West.

Ukraine, although not NATO-member, long sought closer ties to the West and its militaries. Since 2014, when Russia annexed Crimea and supported separatists in Ukraine’s eastern region, it has been in conflict with Russia.

Russia strongly opposes NATO membership of Ukraine. The Kremlin resisted the idea of Ukraine joining NATO.

When Lukashenko was asked what joint actions he meant, the Kremlin replied: “These actions are measures that ensure security for the two of us.”

According to the Kremlin, Putin repeatedly mentioned the problem of NATO infrastructure being expanded on Ukrainian territory. “He” has also stated that this would go against the red lines that he had previously spoken about.”

Dmytro Kuleba (Ukrainian Foreign Minister) rejected the suggestion of a Russian red line outside Russia’s borders. He said Kyiv still had security issues to consider.

He tweeted, “Putin’s red lines are only Russian borders.” “On the Ukrainian-Russian frontier, we have the ability to decide for ourselves how to act in the best interests of both the Ukrainian population and the safety of Europe.