To enter the United States of America, a passport valid for the duration of stay is required by nationals in the chart above.

A general certificate of health is not required by CDC for pet cats and dogs entering the United States, although some airlines or states may require them. Certain states require vaccination for rabies, check with state and local health authorities at your final destination. Dogs must have a certificate showing they have been vaccinated against rabies greater than or equal to 30 days prior to entry into the United States, unless they're coming from rabies free countries. All pet cats and dogs arriving in the state of Hawaii and the territory of Guam are subject to locally imposed quarantine requirements. Many animals are not allowed to be brought into the USA; you can find a complete list on the US Customs and Border Protection website (www.cbp.gov).

All persons, including US citizens, travelling by air, land, or sea between the USA and Canada, Central and South America, the Caribbean and Bermuda are required to present a valid passport, or other approved document, when entering or re-entering the USA.

All travellers entering the USA under the Visa Waiver Program must have an e-Passport with an embedded electronic chip. Any traveller not in possession of an e-passport will require a valid USA entry visa.

If you're an ESTA applicant, you will get an answer within 72 hours.

For other visa types, the length of time it takes to process your visa varies widely. At the US Embassy in the UK, you are advised to allow 60 working days from the date of the visa interview for your application to be processed.

US Customs and Border Protection requires that visitors from abroad substantiate they have sufficient funds to enter the USA. The amount is not a fixed number, however, and does not have to be solely in cash; credit cards, traveller's cheques and other currency equivalents are considered. For more information, check the USCBP's website (www.cbp.gov).

Citizens of visa waiver countries may not apply to extend their stay. Citizens of other countries must file a request with US Citizenship and Immigration Services using Form I-539; the form must be submitted prior to the expiration of the original visa.