The U.N. Security Council is approving a groundbreaking international investigative body that will be allowed to establish who is responsible for chemical attacks in Syria for the first time.

Until now, the U.N. and the global chemical weapons watchdog were only able to investigate attacks without laying blame on the government or rebels.

The new body is the result of rare cooperation between the United States and Russia on Syria.

A council diplomat says the body was approved when no council member objected to a letter that is expected to be sent Thursday to Secretary-General Ban Ki-moon supporting his recommendation for the joint investigative mechanism.

The diplomat spoke on condition of anonymity because they were not authorized to speak publicly.