John Strand, a Copenhagen-based technology consultant said on Friday: "This seems like an extension of American security in the aftermath of 9/11."
"People will ask: 'Do the Americans want to control the internet?'"
The United States announced the move on Thursday, publishing a four-paragraph statement online, saying it would retain - indefinitely - oversight of the computers that control traffic on the internet, instead of gradually releasing control to an international body, as some countries have favoured.
That ran counter to previous US policy, although Michael Gallagher, assistant secretary for communications and information at the Commerce Department, said it was "the foundation of US policy going forward".
He said the declaration was a response to growing security threats and increased reliance on the internet globally for communications and commerce.
That has done little to allay fears that the United States is overstepping its boundaries and locking its grip on the internet - which is used for everything from selling second-hand shoes to criticising governments including authoritarian dictatorships.
Confrontational US move
Patrik Linden, a spokesman for the Swedish Internet infrastructure foundation, which runs and develops the Swedish top level domain .se, said the US announcement was "rather confrontational" towards those who would like to see an international body take control of the internet root servers.
"This kind of statement doesn't exactly favour that discussion," Linden said, adding that the announcement "wasn't completely unexpected".
"This is perhaps what a lot of people have thought that [the US] has always intended," he said.
The US does not have direct control of the internet.
The US controls the administration
of 13 root server computers
Instead, it controls the administration of 13 computers - known as root servers.
The root servers tell web browsers such as Firefox or Internet Explorer and email programmes how to direct internet traffic.
Though located in private hands around the world, they contain government-approved lists of the 260 or so internet suffixes, such as .com, .net and country designators such as .fr for France or .no for Norway.
Patrik Faltstrom, one of Sweden's foremost experts on IP technology and a liaison for both the Internet Engineering Task Force and Internet Architecture Board, said the US announcement was negative for a lot of countries.
"It's not going to work in the long run to have the USA deciding everything by themselves," Faltstrom said. "It's clearly not good if one country can say no to what (DNS changes) are made in Sweden, for example. No country should be able to say no to that."
While the United States has yet to deny such requests, "the mere possibility of being able to do so is pretty serious", Faltstrom said.
"It becomes politics at a high level," he said. "It can only be worked out between the different countries. I don't see any technology in this."
In Japan, officials said the use of the internet for business and commerce - and keeping it available to all - would be debated further in light of the US decision.
"When the internet is being increasingly utilised for private use, by businesses and so forth, there is a societal debate about whether it's befitting to have one country maintaining checks on that. It's likely to fuel that debate," said Masahiko Fujimoto of the Ministry of Internal Affairs and Communications' data communications division.
In 1998, the Commerce Department selected a private organisation with international board members, the Internet Corporation for Assigned Names and Numbers, to decide what goes on those lists.
"It becomes politics at a high level. It can only be worked out between the different countries. I don't see any technology in this"
Swedish liaison officer, The Internet Engineering Task Force and Internet Architecture Board
But Thursday's declaration means the department will keep control over that process rather than ceding it to ICAAN as originally intended.
Fracturing the internet
The US government has historically played the role of overseer because it funded much of the internet's early development.
Critics contend that in a worst-case scenario, countries refusing to accept US control could establish their own separate Domain Name System, thereby fracturing the internet, with addresses in some regions becoming unreachable in others.
Strand said that was unlikely, given the internet's reach and users' familiarity with it. "It's so huge and so solid that's it unlikely anyone would want to do that," he said.
"AOL tried to connect an internet on the internet and it didn't work. There can't be any walled gardens."
A United Nations panel is to release a report this month on internet governance, addressing such issues as oversight of the root servers, before November's UN World Summit on the Information Society in Tunisia.
Some countries have pressed to move oversight to an international body, such as the UN International Telecommunication Union.