Russian President Vladimir Putin.

Senior Russian and NATO military chiefs on Friday held their first phone talks since ties between the two sides collapsed over the crisis in Ukraine, the Defense Ministry in Moscow said.

The chairman of the NATO Military Committee Petr Pavel called Russia’s Chief oOf Staff Valery Gerasimov to discuss the possible restarting of military coordination and avoiding clashes, a statement from the ministry said.

“This is the first high-level military contact since the NATO council took the decision to freeze relations with Russia,” it said.

“The two sides exchanged opinions about current security issues, the prospects of reestablishing military cooperation and avoiding incidents.”

Moscow said Gerasimov used the opportunity to complain about “the significant increased military activity of the alliance near the Russian border.”

NATO headquarters in Brussels confirmed the talks and said “active military to military lines of communications are in the mutual interest of NATO and Russia and they remain open.”

“The two generals agreed that they would remain in contact,” it said, without giving any details about what was discussed.

NATO is beefing up its presence in eastern European allies badly rattled by a more assertive Russia following the seizure of Crimea from Ukraine in March 2014.

NATO severed military contacts with Moscow over its meddling in Ukraine but diplomats and civilian leaders from the two sides have met.

The talks come as the new US administration under Donald Trump seeks to reassure NATO allies that it remains fully committed to the alliance despite pushing other members to spend more on defense.