Türkiye, Saudi Arabia, and Pakistan are expected to sign a joint defense agreement in Mecca on Friday, regional sources and a Turkish official told Reuters. The agreement would deepen security cooperation among three major Sunni Muslim countries with longstanding ties to the United States. Saudi Arabia and Pakistan already have a defense agreement that treats an attack on either country as an attack on both. The three countries have also expanded bilateral defense cooperation in recent years through military training, weapons deals, and joint security initiatives. The anticipated three-way agreement is the culmination of nearly a year of negotiations over broader regional security cooperation.