Ideally, you should not try to enter United States without a visa. However, you can do so if you are a citizen of a nation that comes under the US Visa Waiver Program (VWP). The VWP permits citizens of 38 countries to travel to America for up to 90 days without a visa.
These countries include Australia, Germany, Austria, Denmark, Belgium, Iceland, Japan, Italy, Spain, Norway, UK and many others. Under the VWP, you are allowed to travel only for tourist and business purposes.
However, you need to have an ESTA and valid e-visa, prior to boarding any US-bound sea or air carrier. The ESTA is an Electronic System of Travel Authorization, administered by the US Department of Homeland Security (DHS). It is advisable to apply for an ESTA at least 3-4 days prior to leaving your home country.
You can apply for your ESTA on this website. The online application process is very simple and convenient.
It is important that you have a valid e-passport for travelling to US with an ESTA. An e-passport is embedded with an electronic chip that contains all the details of the passenger. Make sure you check your ESTA status and validity of your e-passport before planning to visit the US. Also, remember that you can’t extend your stay or change the status of your visa when travelling with an ESTA.