The United States turned the tables on Russia this week, accusing them of intentionally violating an agreement intended to maintain the peace between the two military powers over Syria.

“Russia is failing to genuinely de-conflict airspace in Syria. Some of these incidents are not mistakes,” Chief Pentagon Spokesperson Dana W. White told reporters on Monday. “We are working to address this issue at the highest levels,” she added.

For months now, the Russian government has levied unsubstantiated accusations at the U.S. military in Syria, claiming American forces have been aiding the Islamic State, despite actively working to combat them in neighboring Iraq. On two occasions in recent weeks, Russian officials had their misinformation efforts in this regard exposed: the first after the Russian Foreign Ministry tried to pass video game footage off as “evidence” of their claims, and the second when their account of an engagement between a Russian Su-35 and an American F-22 proved to be fictitious.

Secretary of Defense James Mattis also weighed in on the frequency of Russian jets crossing over the Euphrates River in Syria, which serves as the de-confliction line between U.S. and Russian-backed forces within the embattled nation. Russia has been providing military support to the Syrian President Bashar al-Assad’s regime, while U.S. forces have been backing militant groups in the fight against ISIS. Once not engaged in the war on terror, Assad’s regime and those groups have been embroiled in a bloody civil war.