Jens Stoltenberg met Polish Prime Minister Donald Tusk and his British counterpart, Rishi Sunak, at the 1st Warsaw Armoured Brigade base on Tuesday.
At a press conference, Stoltenberg spoke about the threat from Russia and support for Moscow offered by other countries.
"We live in a more dangerous world," he said. "Authoritarian powers are increasingly aligned. Russia is receiving support for its war of aggression from China, Iran and North Korea.
"This reminds us that security isn't regional. Security is global," he said.
Stoltenberg added that Nato was a defensive alliance, not seeking conflict with Russia. At the same time, he went on to say that the alliance intends to provide security to Nato countries.
According to him, the soldiers stationed in Poland were a message that Nato will defend its allies.
"The ten thousand Nato troops based in Poland send an unmistakeable message that Nato will defend and protect all allies," Stoltenberg said.
The Nato chief also stressed Poland's role in providing military capabilities to Ukraine and hosting refugees.
Moreover, he commented that Nato was committed to making Ukraine's assistance more stable and referred to current work on long-term financial aid plans.
Stoltenberg also welcomed the recently adopted US military aid package, which had been stuck in US Congress for months over a dispute between Republicans and Democrats.
He added that Nato also took measures to enhance Ukrainian air defence with more Patriot systems from Germany. (PAP)
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