Originally Posted by
GUWonder
Yes, it's possible, when done in person at US embassies/consulates
It turned out that I don't have to travel on short notice now. And as my US passport is still good until July, and my Swiss passport is brand new, I figure I don't have to renew the US passport until after my April trip. The US passport will be valid less than 3 months, but I only need it to enter and leave the US. The rest of the trip, I can be Swiss.