Serbia, the only country in Europe that has refused to sanction Russia for its invasion of Ukraine, agreed to supply arms to Kyiv or has sent them already, according to a classified Pentagon document.

The document, a summary of European governments’ responses to Ukraine’s requests for military training and “lethal aid” or weapons, was among dozens of classified documents posted online in recent weeks in what could be the most serious leak of U.S. secrets in years.

Response to Ongoing Russia-Ukraine Conflict,” the document in chart form lists the “assessed positions” of 38 European governments in response to Ukraine’s requests for military assistance.

The chart showed that Serbia declined to provide training to Ukrainian forces, but had committed to sending lethal aid or had supplied it already. It also said Serbia had the political will and military ability to provide weapons to Ukraine in the future.

The document has not been verified.