NATO leaders were preparing Friday to clear the way for the military alliance to deploy more troops in Eastern Europe, while insisting that it is not gunning for conflict with Russia.
"We do not want a new Cold War. The Cold War is history, and it should remain history," NATO Secretary General Jens Stoltenberg said as leaders were gathering in the Polish capital Warsaw for the start of their two-day summit.
"NATO will once again send a very clear message that we are here to protect and defend all allies in a new and more challenging security environment," he added.
The summit comes as relations between NATO and Moscow have hit a post-Cold War low, due to Russia's annexation of the Ukrainian peninsula of Crimea in March 2014 and its support for separatists in eastern Ukraine.
Both sides have been flexing their military muscles in Eastern Europe ever since, accusing each other of sabre-rattling and provocations.
In Warsaw, NATO leaders are due to clear the way for the deployment next year of four battalions of up to 1,000 troops each to Estonia, Latvia, Lithuania and Poland, which feel threatened by Russia's actions in Ukraine.
"Together we have to ensure that everyone who, just for a moment, is tempted to apply the law of force will come to understand very quickly that it simply does not pay off," Polish President Andrzej Duda said at a pre-summit event on Friday.
The multinational battalions will be deployed on a rotational basis, in part to comply with a NATO-Russia agreement from 1997 that requires the alliance to refrain from the "permanent stationing of substantial combat forces" in Eastern Europe.
The United States will lead the battalion in Poland, to which it will contribute around 1,000 soldiers, President Barack Obama said in Warsaw. Britain will take the lead in Estonia, announcing on Friday that it will provide 500 troops there.
Germany will head the battalion in Lithuania, while Canada is expected to lead in Latvia.
Other NATO nations will also contribute troops, with Danish Prime Minister Lars Lokke Rasmussen announcing that his country will send up to 200 soldiers to Estonia.
The deployment is irking Moscow, which has repeatedly warned that an eastward NATO expansion threatens its national security. The Kremlin on Friday slammed the Western military alliance for being short-sighted and having a misguided focus on threats from Russia.
"If they need to ... stir up anti-Russian hysteria and Russophobia, then based on that emotion-evoking backdrop deploy air and ground forces close to Russia's borders, it is unlikely that we can find some reason for collaboration," the Kremlin's spokesman Dmitry Peskov said in comments carried by the Interfax news agency.
Some Russian officials have threatened a military response, but Polish Foreign Minister Witold Waszczykowski dismissed as "absurd" suggestions that NATO has been acting threateningly.
"It's Russia that is pursuing the whole time an imperial policy," he said.
Moscow is also likely to be irritated by progress made on NATO's missile defence system in Europe. Command and control over the system will be handed from the United States to NATO at the summit. Moscow believes that it could be used to shoot down Russian missiles.
Britain's vote to leave the EU is also casting a shadow over the summit, although officials have been at pains to argue that the move will not affect the British NATO membership.
"Britain may be leaving the EU, but we are not turning our back on ... European defence and security," British Prime Minister David Cameron said as he arrived in Warsaw.
"I'm absolutely certain that the UK will continue as a strong and committed ally in NATO," Stoltenberg added.