NATO would currently be unable to protect the Baltics against a Russian attack, the commander of US ground forces in Europe, General Ben Hodges, said in a news report Wednesday.
"Russia could take over the Baltic states faster than we would be able to defend them," Hodges was quoted as saying in a German-language article by news weekly Die Zeit.
The general said he agreed with an assessment by military analysts who claimed that Russian forces could conquer the capitals of Baltic states Latvia, Lithuania and Estonia within 36 to 60 hours.
Hodges also said NATO forces had found numerous deficiencies during the recent "Anaconda" military exercise in Poland, according to the article from Thursday's edition of Die Zeit, released early to AFP.
Heavy military equipment could not be moved fast enough from western to eastern Europe, said the general, who also voiced concern about the alliance's communication technology.
"Neither radio communication nor email are secure," he was quoted as saying. "I assume that everything I write on my BlackBerry is being monitored."
The Anaconda maneuver included troops from more than 20 NATO member states but was officially a Polish national exercise.
Hodges told Die Zeit that "some countries, like France and Germany, thought it would be too provocative toward Russia to call it a NATO exercise".
Thousands of NATO troops hit the ground in Poland in the massive 10-day show of force as the alliance launched its biggest war games in eastern Europe since the Cold War.
Russian President Vladimir Putin on Wednesday hit out at NATO for "stepping up its aggressive rhetoric and its aggressive actions close to our borders".
He said that Moscow was therefore "obliged to dedicate special attention to resolving tasks connected with heightening the defense capabilities of our country".
'Boost NATO's eastern flank'
NATO announced last week that it would deploy four battalions to the Baltic nations and Poland to counter a more assertive Russia, ahead of a landmark summit in Warsaw on July 8-9.
All four countries were once ruled from Moscow and remain deeply suspicious of Russia's intentions.
Russia bitterly opposes NATO's expansion into its Soviet-era satellites and last month said it would create three new divisions in its southwest region to meet what it described as a dangerous military build-up along its borders.
Putin, speaking Wednesday on the 75th anniversary of Nazi Germany's invasion of the USSR, accused the West of rejecting overtures from Russia to help tackle the common foe of "international terrorism" -- as it once ignored the Soviet Union's warnings about Hitler -- while seeking to isolate Moscow over the Ukraine crisis.
"We once again, as it was on the eve of World War II, are not seeing a positive response," Putin said.
Relations between Russia and the West have slumped to their lowest point since the Cold War over Moscow's 2014 annexation of Crimea from Ukraine and its alleged masterminding of a separatist uprising.
Fears of Russian expansionism have rattled NATO's former eastern bloc members and prompted the US-led alliance to bolster its presence along its eastern flank.
Following talks in Berlin Thursday, both German Chancellor Angela Merkel and Poland's Prime Minister Beata Szydlo stressed the importance of boosting security on the border with Russia.
"Germany has always sought dialogue with Russia," Merkel said, but added that on the other hand, "Germany also sees the necessity to boost NATO's eastern flank".
"That's why we are taking on additional responsibility in Lithuania, that's why we took part in the Anaconda manuever," she said.
Szydlo said that the moves are not only aimed at shielding her country and the Baltic states, but at protecting all of Europe.