The US government has started asking visitors from countries that have a visa waiver arrangement with it to provide details of their social media accounts when applying for the waiver.
A report on the website Politico said the practice, which iTWire reported about in June, had begun on Tuesday this week.
Australia is among the 38 countries that have a visa waiver agreement with the US; prospective visitors have to visit the electronic system for travel authorisation (ESTA) website and apply for a waiver before they travel.
(Australian journalists who are visiting the US on a reporting assignment, and certain other categories of travellers, have to obtain an I class visa.)
{loadposition sam08}The Politico report said the move was aimed at spotting potential terrorist threats.
A government official confirmed on Thursday that a dropdown had been added to the ESTA form, with an "optional" request to "enter information associated with your online presence".
It asked for details of social media accounts, including Google+, Instagram, Facebook, YouTube and LinkedIn.
Critics of the move are unhappy that it has been adopted. The Internet Association, which represents technology companies including Google, Facebook and Twitter, had united with consumer advocates to advance the argument that the new measure threatened free expression and posed additional privacy and security risks to visitors.
The Politico report quoted Internet Association general counsel Abigail Slater as saying: "Democratic and non-democratic countries — including those without the United States’ due process protections — will now believe they are more warranted in demanding social media information from visitors that could jeopardise visitors' safety.
"The nature of the DHS' requests delves into personal information, creating an information dragnet."
The US government approved the new measure on 19 December.