Following the killing of Iranian military and intelligence commander Major General Qassem Soleimani in Baghdad in a drone attack carried out by the United States, the Iranian government registered its protest with the Swiss Embassy in Tehran. 

• Switzerland represents the interests of the US in Iran. This is because the US itself does not have an embassy there. Iran’s interests in the United States, on the other hand, are represented by the Pakistan Embassy in Washington. 
• In an arrangement such as this, Switzerland is the “Protecting Power” of the United States’ interests in Iran. The instrument of Protecting Powers is provided for under the 1961 and 1963 Vienna Conventions on Diplomatic Relations.  
• “If diplomatic relations are broken off between two States, or if a mission is permanently or temporarily recalled… the sending State may entrust the protection of its interests and those of its nationals to a third State acceptable to the receiving State,” the 1961 Vienna Convention states.  

• And the 1963 Convention reiterates: “A sending State may with the prior consent of a receiving State, and at the request of a third State not represented in the receiving State, undertake the temporary protection of the interests of the third State and of its nationals.” 

Source: Indian Express