Nato is set to more than double the size of its response force due to Russian actions in Ukraine and the challenge of Islamic extremism, the head of the military alliance announced.
Speaking before the opening of a meeting of defence ministers in Brussels, Nato secretary-general Jens Stoltenberg said they are expected to agree to boost the size of the force from 13,000 to 30,000.
He said US defence secretary Chuck Hagel and other attendees are also expected to approve details for the establishment of a new ultra-fast joint task force of about 5,000 troops.
In addition, ministers should give the green light to a proposal to create Nato command and control liaison centres in the three Baltic republics and Poland, Romania and Bulgaria - Nato members states that feel especially vulnerable to aggressive moves from Moscow.
"Our decisions make clear that Nato is determined to defend all allies against any threat, from any direction." Mr Stoltenberg said. Asked if the US-led alliance's latest decisions might fuel a Cold War-style escalation with the Kremlin, Nato's top civilian official said the measures are purely defensive and are being taken only because of Russia's actions.
"In Ukraine, violence is getting worse and the crisis is deepening," Mr Stoltenberg said. "Russia continues to disregard international rules and to support the separatists with advanced weapons, training and forces."
Russia has vehemently denied allegations of its involvement in the Ukrainian conflict. The Kremlin acknowledged that Russian volunteers are fighting in eastern Ukraine but insists that Moscow has not sent its troops or weapons to help the rebels.
Russia has expressed concerned about Nato's build-up in eastern Europe while defending a heavy military presence at its border with Ukraine.
On Saturday, Mr Stoltenberg is scheduled to hold his first meeting as Nato secretary-general with Russian foreign minister Sergey Lavrov in Munich.
Asked what he will tell Mr Lavrov, Mr Stoltenberg said, "The important thing for Nato of course is to underline that Russia is responsible for violating international law, for violating the sovereignty, the territorial integrity of Ukraine, annexing Crimea, destabilising eastern Ukraine.
"We are calling on Russia to stop support for the separatists and to respect the Minsk agreement and to use all its influence on the separatists to make them respect the ceasefire," Mr Stoltenberg said.