It depends on how long you intend to stay. Your passport must not expire during your visit, but if for some unforseen reason it appears likely to happen, or it does happen, contact the US Embassy or Consulate IMMEDIATELY. While, technically, you might not be breaking any US laws, you would certainly be in violation of Australian law and liable for prosectuion under their judicial system.
How long needed on passport to travel to FinlandFinland
UK passport holders require 6 months left on their passport
As long as you have a passport and the Australian Government has no objection to you entering the country you can get into Astralia.
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You don't need a passport to travel between the UK and the Republic of Ireland.
It must at least have three months left.
You need at least 3 months left from the time that you depart for US. But many countries need at least 6 months left of passport validity for international travel.
You can travel immediately after acquiring a passport.
According to the State Department website and the airlines (USAirways) your passport just needs to be valid for your travel dates. As long as you are back before your passport expires, you are OK.
depends on duration of stay, if passport expires in 2 weeks, and you stay in Hungary for 3 weeks - problem!
A person may still travel to any country as long as the passport is not expired. How long before it expires is not taken into account unless the passport expires before the traveler is expected to return.
Usually at least six months but it may differ by country.