SEOUL, South Korea (AP) — A new agreement between Russia and North Korea reached by their leaders requires the countries to use all available means to provide immediate military assistance in the event of war, North Korean state media said.

The North’s official Korean Central News Agency on Thursday reported the language of the comprehensive strategic partnership agreement reached by its leader Kim Jong Un and Russian President Vladimir Putin in Pyongyang on Wednesday. The agency said Article 4 of the agreement states that if one of the countries gets invaded and is pushed into a state of war, the other must deploy “all means at its disposal without delay” to provide “military and other assistance.”

The deal could mark the strongest connection between Moscow and Pyongyang since the end of the Cold War. Both Kim and Putin described it as a major upgrade of their relations, covering security, trade, investment, cultural and humanitarian ties.

The summit came as the U.S. and its allies expressed growing concerns over a possible arms arrangement in which Pyongyang provides Moscow with badly needed munitions for its war in Ukraine, in exchange for economic assistance and technology transfers that could enhance the threat posed by Kim’s nuclear weapons and missile program.