14 CFR §61.41

1. (a)A person may credit flight training toward the requirements of a pilot certificate or rating issued under this part, if that person received the training from:
   1. (1)A flight instructor of an Armed Force in a program for training military pilots of either—
      1. (i)The United States; or
      2. (ii)A foreign contracting State to the Convention on International Civil Aviation.
   2. (2)A flight instructor who is authorized to give such training by the licensing authority of a foreign contracting State to the Convention on International Civil Aviation, and the flight training is given outside the United States.
2. (b)A flight instructor described in paragraph (a) of this section is only authorized to give endorsements to show training given.