Washington/Kiev, May 18 (IANS/DPA): Kiev is at a disadvantage in its defence against Russian forces due to restrictions on using US weapons against targets on Russian soil, according to the Washington-based Institute for the Study of War (ISW).

The latest report from the US think-tank released on Friday says that Russia exploits these restrictions by launching attacks from protected areas near the Ukrainian border.

Ukraine President Volodymyr Zelensky has called for permission to use US weapons on Russian territory but was currently denied by the US to avoid further escalation.

The US approach to date has severely limited Ukraine's ability to defend itself against Russian attacks in the north of the Kharkiv region, it said.

According to the Pentagon, the US is providing the weapons so that Ukraine can liberate its occupied territories, but not for attacks on Russia.

Ukraine's goal is to attack bases in Russia with Western weapons to destroy them even more effectively than with its own less powerful drones and missiles.

Russia, on the other hand, is warning of an escalation in the war if weapons from NATO countries are used against them.