2 Reasons NOT to Set Up a Naval Blockade around Iran

I’ve been divided over whether or not to blockade Iran. It sounds extreme, but I couldn’t find any solid argument against it. But now I've made my decision over a blockade. We shouldn't do it. For 2 reasons:

1. It would consume too many resources
Our navy may not be as heavily involved in Iraq and Afghanistan as, say, the Army, but we do have a budget deficit, and I'm sure this would not help.

2. Would we attack our allies?
Iran is still the 4th largest exporter of crude oil. What would we do if China, Russia, or even France needed that oil and tried to bypass our blockade? Would we sink them? Capture their ship? How many enemies does the U.S. need?