"Russia's capacity to produce military equipment has increased tremendously," Poulsen said, as quoted by the Reuters news agency.
"It cannot be ruled out that within a three- to five-year period, Russia will test Article 5 and NATO's solidarity," he warned. "That was not NATO's assessment in 2023. This is new knowledge that is coming to the fore now," he told the Jyllands-Posten newspaper on Friday.
His warning came after other European NATO countries have made similar warnings in recent weeks, Reuters reported.
Germany's Defence Minister Boris Pistorius said in January that the alliance should prepare for a Russian attack on a NATO country within five to eight years, according to Reuters.
Poulsen also said on Friday that the alliance could face hybrid attacks in an effort by Russia to destabilize a member country.
"Russia potentially has the will to do so," he said. "Now they can also have the ability to have a military capability earlier than we expected. There is reason to be genuinely concerned," he added.
Polish Defence Minister Władysław Kosiniak-Kamysz said last week that his country must urgently prepare for the threat of war with Russia.
"I expect every scenario and take the worst ones most seriously," Kosiniak-Kamysz said when asked in a media interview whether he was worried that Russia would defeat Ukraine and subsequently invade Poland.
Władysław Kosiniak-Kamysz. Photo: P. Chmielewski/Polish Radio
Russia invaded Ukraine on February 24, 2022, starting the largest armed conflict in Europe since World War II.
Monday is day 719 of Russia’s war on Ukraine.
Source: IAR, PAP