PRESIDENT Rodrigo Duterte has appointed Senator Alan Peter Cayetano as secretary of the Department of Foreign Affairs (DFA).

In a departure press conference at the Ninoy Aquino International Airport-Terminal 2 in Pasay City, Duterte said he signed Cayetano's appointment paper earlier Wednesday before heading to Cambodia.

"Here in DFA, I remember, I signed an appointment [paper] just now before I left my room and I saw the name of Senator Cayetano in the DFA," Duterte told reporters.

"I signed it this afternoon," he added.

Cayetano was Duterte's running mate in last year's presidential race.

Cayetano's entry to the Cabinet came after the one-year election ban on appointing losing candidates in the May 2016 polls expired on Wednesday.

Duterte earlier assigned Undersecretary Enrique Manalo as acting DFA secretary after the Commission on Appointments rejected the ad interim appointment of Perfecto Yasay Jr. due to questions about his citizenship.

Cayetano is currently in Geneva, Switzerland, to defend Duterte's war on illegal drugs before the United Nations. (SunStar Philippines)