Interest Section

An interest section is a diplomatic arrangement used when two states have broken off formal relations but still need a channel for consular services, citizen protection, and limited negotiation. Rather than maintain an embassy, the sending state operates a small office physically housed within, and nominally under the flag of, a third country's embassy — known as the protecting power. Staff may be diplomats of the sending state or, in more restrictive arrangements, employees of the protecting power itself.

The practice is grounded in Article 45 of the 1961 Vienna Convention on Diplomatic Relations, which permits a state whose mission has been withdrawn to entrust the protection of its interests and premises to a mutually acceptable third state. Interest sections typically handle visas, passport renewals, notarial services, prisoner welfare visits, and back-channel political messaging. They are usually smaller than full embassies and operate under tighter restrictions on travel and contacts within the host country.

The best-known modern example was the U.S. Interest Section in Havana, which functioned within the Swiss Embassy from 1977 until 2015, when relations were restored and it was upgraded to a full U.S. Embassy. Cuba operated a reciprocal interest section in Washington under the Swiss flag during the same period. Other notable cases include the U.S. Interest Section in Tehran, hosted by Switzerland since 1980, and the British Interest Section in Tehran, which has at various points operated under Swedish protection.

Interest sections occupy a useful middle rung on the diplomatic ladder: they signal that relations are formally broken while preserving a working channel. Upgrading or downgrading the arrangement — for instance, raising it to a liaison office or full embassy — is itself a calibrated political signal.