The statement came from Department of State Spokesman Victoria Nuland, Gun.Az reported.
Nuland disclosed the response given to the letter requesting to give support to the struggle of South Azerbaijan for freedom from Iran and Azerbaijan's unification.
The Department of State official also responded to questions of reporters regarding the separation of countries' territories.
"Our position is known. The United States advocates the principle of territorial integrity."
In the letter addressed to Hillary Clinton, US Congressman Rohrabacher wrote that the majority of Azerbaijanis call on to unify their motherland which was divided into two parts 200 years ago.
"The number of ethic Azerbaijanis in Iran is twice more compared to the Republic of Azerbaijan. This country was created in 1991, following the collapse of 1991, and now it is time for Iranian Azerbaijanis to gain their freedom," the congressman writes.
"To support rightful desires of the Azerbaijani people in the struggle for independence is in and of itself a good deed. At the same time, this is a bigger danger for the Tehran regime than bombing their underground nuclear bunkers," he noted in the end of the letter.