Brussels - Four international battalions stationed in eastern Europe are now ready to respond to any Russian "aggression", the defence ministers from eight NATO countries said on Thursday.Germany, Britain, the United States and Canada currently lead four multi-national "battlegroups" in Estonia, Latvia, Lithuania and Poland, as tripwires against possible Russian adventurism."Today, we declare that (these battalions) are ready and able to deter and, if necessary, immediately respond to any aggression in concert with national forces underpinned by a viable reinforcement strategy," the defence ministers said in a joint statement at a Brussels summit.Under a programme called the Enhanced Forward Presence (EFP), NATO deployed the battalions in Poland and the Baltic states, a region formerly under Moscow's control, following alarm over Russian actions in Ukraine and Syria.Adding to tensions, Russia is preparing massive military exercises in its west in September, and has deployed a missile system in the neighbouring enclave of Kaliningrad.NATO agreed at a 2016 summit in Warsaw to boost NATO's military presence along the alliance's eastern flank.The four battalions, which deploy on a rotational basis, total about 4 500 troops from 15 member nations and train constantly to improve co-ordination and conduct joint exercises.The EFP "is a direct response to Russia's aggressive actions, including provocative military activities in the periphery of NATO territory, which have reduced stability and security, increased unpredictability, and changed the security environment," the joint declaration said.United NATO"We welcome the fact that we are making progress both when it comes to our enhanced forward presence in the Baltic States and Poland," NATO Secretary General Jens Stoltenberg said Thursday."And we continue to strengthen our presence in the Black Sea region."US Defence Secretary Jim Mattis last month visited the German-led battlegroup in Lithuania, where he saw troops from Belgium, Norway, America and other nations show off tanks and other gear. "This is a profound example of a united NATO," Mattis said at a meeting with his German counterpart Ursula von der Leyen on Tuesday, when he announced ongoing US support for the initiative through 2020."Our alliance has long been a stabilising force in Europe. It helps preserve the rules-based international order."Separately, the United States, Britain and Norway signed a joint statement of intent to lay out "guiding principles" for a trilateral partnership with their P-8A Poseidon submarine hunters "to address the changing security environment in the North Atlantic".