Ukraine has already changed some of its military plans due to the leak of classified US documents, writes CNN.

The news outlet notes that secret Pentagon documents posted online in recent weeks show how the US is spying on both allies and adversaries, which has deeply concerned American officials who fear that the revelations could jeopardise sensitive sources and compromise important international relations.

Some of the original documents expose the extent of US wiretapping of key allies, including South Korea, Israel, and Ukraine.

Others reveal the extent of US penetration of the Russian Defence Ministry and the Russian Wagner PMC, largely through intercepted communications and human sources that could now be cut off or jeopardised.

Others expose key weaknesses in Ukrainian weapons, air defence, battalion strength and readiness at a critical point in the war, when Ukrainian forces are preparing to launch a counteroffensive against the Russians, and just as the US and Ukraine have begun to develop a more trusting intelligence-sharing relationship.

Ukraine has already changed some of its military plans because of the leak, a source close to Ukrainian President Volodymyr Zelensky told CNN.