NATO's top general has suggested the alliance should establish a military presence in Bulgaria and Romania following Russia's troop build-up near the border with Ukraine, German newspaper Spiegel reported Saturday.

It said the proposals made by Tod Wolters, NATO's Supreme Allied Commander Europe, would in effect expand the alliance's "Enhanced Forward Presence" mission under which it has deployed military forces to the Baltic states and eastern Poland.

Der Spiegel did not directly quote Wolters. It said it had "information" that Wolters had "called for a reinforcement of troops on the eastern border" of NATO during a video link with military chiefs of "partner nations."

It said the plan would in effect "expand NATO's presence (to Romania and Bulgaria) through the Enhanced Forward Presence (EFP) mission."

NATO declined to comment on Der Spiegel's report. Extending NATO's presence to Bulgaria and Romania is something that both countries have called for.

NATO Secretary-General Jens Stoltenberg said Friday that NATO would "constantly assess the need to further adjust our posture, our presence, also in the Southeast of the region, because we need to be sure that we can always protect and defend allies against any threat."

Russia's military build-up near Ukraine has increased tensions between Moscow and NATO and the alliance has urged Russia not to invade the former Soviet republic.

Russia denies planning an invasion. It says it is responding to what it sees as threats to its own security from Ukraine's increasingly close relations with NATO and aspirations to join the alliance.

Moscow said Friday it wanted a legally binding guarantee from NATO that it will give up any military activity in eastern Europe and Ukraine.