Cheers as US troops enter Poland, Russia decries threat to their national security

American soldiers are rolling into Poland, fulfilling a dream many Poles have had since the fall of communism in 1989 to have US troops on their soil as a deterrent against Russia.

US army vehicles and soldiers in camouflage crossed into south-western Poland on Thursday morning from Germany and were heading for Zagan, where they will be based.

The US and other Western nations have carried out exercises on Nato's eastern flank, but this US deployment will be the first continuous deployment to the region by a Nato ally.

Responding to the move, the Kremlin said it was concerned by what it described as a U.S. military build-up in Poland, saying the move represented a threat to its national security.

Despite the celebrations by some Poles, a cloud also hangs over the historic moment: anxieties that the enhanced security could eventually be undermined by the pro-Kremlin views of President-elect Donald Trump.

Poland and the Baltic states are nervous about Russian assertiveness displayed in Ukraine and Syria.

Some people waved and held up American flags as US troops in tanks and other vehicles crossed into south-western Poland from Germany. Poland's prime minister and defence minister will welcome them in an official ceremony on Saturday.

“This is the fulfilment of a dream,” said Michal Baranowski, director of the German Marshall Fund think tank in Warsaw. “And this is not just a symbolic presence but one with a real capability.”

It is part of a larger commitment by President Barack Obama to protect a region that grew deeply nervous when Russia annexed Crimea from Ukraine in 2014 and then began backing separatist rebels in Ukraine's east.

Poland and the Baltic states also feel threatened by Russia's recent deployment of nuclear-capable Iskander missiles in Kaliningrad, the Russian territory wedged between Poland and Lithuania.

But Russia says it is the one who is threatened.

“These actions threaten our interests, our security,” President Vladimir Putin's spokesman Dmitry Peskov said.