NATO announced Friday it will hold its next summit in Warsaw on July 8-9 next year as it tackles perceived threats from Russia to the east and jihadists to the south.

The Polish capital is the former host of the Warsaw Pact, the anti-NATO alliance between Moscow and its eastern satellites that existed until the Soviet bloc collapsed in 1991.

At their last summit in Wales in September NATO leaders agreed to bolster the alliance's eastern defences amid charges that Russia has provided troops and equipment to support Kremlin-backed separatists in eastern Ukraine.

"This summit comes at a crucial time for the alliance, as the tectonic plates of Euro-Atlantic security have shifted both in the east and the south," Secretary General Jens Stoltenberg said in a statement.

"We are already implementing the biggest reinforcement of our collective defence since the end of the Cold War," Stoltenberg said.

Leaders of the 28 NATO countries, including military superpower the United States as well as former Soviet satellite countries in the east, will determine how to adapt best to the perceived new threats, he said.

"NATO remains ready to defend all allies against any threat from any direction," he added.

The Baltic states of Lithuania, Latvia and Estonia -- which were under Soviet rule from the end of World War II to 1991 -- now fear Moscow could try to destabilise them to test NATO's commitment to collective defence.

Lithuania said earlier this month that the three will soon formally ask NATO to deploy several thousand troops as a deterrent to Russia.

NATO is also on guard to the south where the militant group Islamic State has made dramatic headway in Iraq and Syria as well as gained a foothold in Libya.

Stoltenberg also said NATO "will stress our long-term commitment to Afghanistan" even though it withdrew bulk of its troops from the central Asian country at the end of 2014.