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I have a US passport plus another passport from my birthplace. I would like to go to Iran for a business trip. Using US passport to enter Iran requires visa and lots of paperwork, but with my other passport it is quite easy, one can apply at the airport. On the other hand, to come back to US I can not use my birthplace passport.
Can I use both passports to travel from US to Iran, one to enter it, and one to come back?
What are the potential problems/issues?
Edit: I have read the other question about traveling with two passports. However, traveling from US to Iran is a bit more special, consider the situation. For example, I found out that there have been some changes in travel policy by US in January, but not sure of details and especially advice from people who have actually made such trips.
For example, the advice was that I show my other passport when leaving the US. But that passport does not allow me to stay legally in the US, since it does not have visa (I had a green card before but the took it away after becoming US citizen).
So do I have to show both passports when leaving US?
Would travel to Iran with two passports cause potential delays when I come back?