Jens Stoltenberg, NATO's Secretary-General, revealed on Thursday that NATO's key document, the NATO Strategic Concept, will omit Russia as the alliance's strategic partner.

In this document, which is expected to be adopted at the Madrid Summit in June, members countries of the alliance reaffirm its values and purpose, present a collective security assessment, delineate challenges and the measures that tackle them, outlining guidelines for NATO's future political and military development.

"The Strategic Concept is NATO's most important document, after our founding treaty, the Washington Treaty. The previous Strategic Concept was adopted in 2010. The world has changed radically since. This should be reflected in the new Strategic Concept. For example, we call Russia a strategic partner in the actual Strategic Concept," Stoltenberg said.

He also highlighted that the Strategic Concept will shift to focus on "a more aggressive Russia", yet reflect other threats, including terrorism, cyberspace, climate change, and technologies.

Stoltenberg further said that NATO must adapt since its success depends on its ability to change in a changing world.

Russia has for months been warning of the threat posed against it by NATO's attempts to expand eastward, which happened simultaneously with an increase in NATO military activity along Russia's borders, and batches of lethal weapons being sent to Ukraine, prompting Russia to request security guarantees from the West. Washington failed to provide the guarantees, leading to the war in Ukraine.