The newly signed Türkiye-Saudi Arabia-Pakistan mutual defence pact could eventually expand to include other countries, with Egypt emerging as the strongest potential candidate.
The agreement, signed in Mecca by the three countries, states that an attack on one member would be considered an attack on all. Turkish Foreign Minister Hakan Fidan has compared the arrangement to NATO's Article 5, although he stressed that the pact is defensive and is not directed against Iran or any other specific country.
Egypt
Egypt appears to be the most likely country to join. Turkish President Recep Tayyip Erdogan has already indicated that Cairo could become part of the alliance in the future. Egypt, Saudi Arabia, Türkiye and Pakistan have also cooperated through the informal R4 framework, making Cairo a particularly significant potential addition.
Egypt would bring one of the Middle East's largest militaries and a strategically important position linking the Mediterranean, Red Sea and Arab world.
Other Gulf countries
Qatar, the United Arab Emirates, Kuwait, Bahrain and Oman could also become potential candidates because of their geographical proximity to Saudi Arabia and their shared security concerns in the Gulf.
However, membership would depend heavily on each country's existing alliances and foreign-policy priorities. Some Gulf states maintain extensive defence relationships with the United States and may therefore be cautious about joining a new collective-defence arrangement.
Azerbaijan
Azerbaijan could also attract attention because of its close strategic and defence relationship with Türkiye. Ankara and Baku already have a formal alliance, including commitments to support each other in the event of threats.
However, there has been no official announcement that Azerbaijan is preparing to join the new pact, so its inclusion remains speculative.
Indonesia and Malaysia
Further afield, Indonesia and Malaysia could theoretically be considered because of their strong relations with Türkiye, Saudi Arabia and Pakistan and their membership in the Organisation of Islamic Cooperation.
But geographical distance and their existing regional commitments make them less obvious candidates than Egypt or neighbouring Gulf states.
What happens next?
The three founding members are expected to establish a ministerial committee and a permanent secretariat in Saudi Arabia to coordinate the alliance. The precise mechanisms for military cooperation and collective defence are expected to be discussed at the group's first meetings.
For now, Egypt stands out as the clearest potential new member, while other countries remain possibilities rather than confirmed candidates. Pakistani Foreign Minister Ishaq Dar has said the agreement is open to other countries committed to peaceful conflict resolution.
If the pact expands, it could become an important new security framework linking South Asia, the Middle East and Türkiye, although analysts caution that it should not yet be regarded as a Middle Eastern version of NATO.