Russian President Vladimir Putin could invade Poland “overnight”. Picture: Alexei Nikolsky/Sputnik, Kremlin Pool Photo via AP

The aggressive foreign policy of a resurgent Russia under president Vladimir Putin has countries in the region on high alert after they annexed Crimea from Ukraine, according to The Sun.

The think tank Atlantic Council warns: “Even if Moscow currently has no immediate intent to challenge NATO directly, this may unexpectedly change overnight.”

It talked up the rapid speed of Russia’s military operations and warned Poland and its allies that they must be prepared and arm up as a deterrent.

The report even suggests potential targets to hit in Russia if required, including the Kaliningrad and the Metro infrastructure in Moscow.

Russian SU-27 jet fighters and MIG 29 jet fighters. Picture: Kirill Kudryavtsev/AFPSource:AFP

It recommends more US missiles be shipped to the region, and urges Poland to find a way to stop ‘fighting age men’ quitting the country to find work abroad, and join their military instead.

Earlier this month, US president Barack Obama announced plans to deploy 1,000 troops to the east of Poland.

It is the biggest escalation of hostilities in the region between Russia and NATO states since the Cold War.

US President Barack Obama announced plans to deploy 1000 troops to the east of Poland. Picture: Matt Dunham/APSource:AP

Ben Rhodes, the deputy US national security adviser, denied that the US was escalating tensions in the region.

He said: “What we are demonstrating is that if Russia continues this pattern of aggressive behaviour, there will be a response and there will be a greater presence in eastern Europe.”

Britain is one of the 28 NATO members and also decided to make deployments this month to the region.

500 troops will be stationed in Estonia and 150 in Poland, and a further 3,000 will be put on notice for immediate action in the region if activity increases.

This article originally appeared on The Sun and was republished with permission.