Warsaw: The United States will deploy 1,000 troops and a separate brigade headquarters to Poland, President Barack Obama announced today, as the NATO alliance shores up its defences in eastern Europe.

The US troops in Poland are part of a larger NATO effort which will see three other battalions led by Canada, Germany and Britain deployed to the three Baltic states to reassure the alliance's eastern allies in the face of a more aggressive Russia.

"As the Alliance prepares to enhance our forward presence in eastern Europe, I can announce that the United States will be the lead nation for the NATO presence here in Poland,"

Obama told reporters as Poland's President Andrzej Duda welcomed him to the NATO summit in Warsaw.

"And that means the United States will deploy a battalion, roughly 1,000 American soldiers here in Poland on a rotational basis to serve shoulder to shoulder with Polish soldiers," he said.

"In addition, when a new US armoured brigade begins rotating through Europe next year, its headquarters will be here in Poland. In other words Poland will be seeing an increase in NATO and American personnel and in the most modern military equipment."

Obama's announcement came as the Atlantic alliance began a two-day summit in the Polish capital, against a backdrop of Russia's intervention in Ukraine and billed as one of the most important such gatherings since the end of the Cold War.