Is the US already at war with Iran? - Request for Information

I have seen it written in various places that a "State of War" already exists between the US and Iran as they have not signed a peace treaty since they were last in conflict. Can this be used as a way to initiate an attack on Iran without any UN resolution, Congressional resolution etc? Is anyone reading this qualified enough in international law to tell us, I cannot find any declared war between the two staes but freely admit to not being qualified in this matter, just worried by what looks like the inevitible slide to conflict. Is this state of war as specious as one such as that existing between Japan & Russia who still have not officially ended WW2?