Problems with the Blackberry smartphone system appear have to spread to the United States.
Users began to report loss of services on Wednesday, with many turning to Twitter to complain about their lack of email.
The latest development follows two days of sporadic blackouts across Europe, the Middle East and Africa.
Blackberry’s owner, RIM, blamed the latest outages on a backlog of emails to Europe from Asia and the Americas.
“It is a backlog issue,” RIM software vice president David Yach told a press conference in Ottawa, Canada.
“Clearly we have a backlog in Europe… as you can imagine, with the global reach of Blackberry and people using it to contact others around the world, there’s a lot of messages to Europe from Asia and the Americas.
“Over time that backlog has built up and affected our other systems.”
As news of the failure in the US spread, one user tweeted: “What is the status here in the USA? I am in New York and there seems to be no email service.”
Another, who lives in Texas, wrote: “My #blackberry is not working! I can dial out that’s it. What’s up?”.
Blackberry had earlier declared services to be “operating normally”, only to be contradicted by frustrated users.
Many called on the phone firm to “sort out” the problems and get the network running again.
RIM acknowledged that it was still experiencing problems and apologised for the inconvenience.
“The messaging and browsing delays… in Europe, the Middle East, Africa, India, Brazil, Chile and Argentina were caused by a core switch failure within RIM’s infrastructure,” a company statement said.
“As a result, a large backlog of data was generated and we are now working to clear that backlog and restore normal service as quickly as possible.”
The blackouts have left millions of users without email, web browsing and Blackberry Messaging (BBM) services.
The cause is believed to be due to server problems at RIM’s UK data centre in Slough.
Blackberry users around the world began reporting problems with their handsets mid-morning on 10 October and at 14:42 BST, Blackberry UK sent out a tweet which said: “Some users in EMEA are experiencing issues.”
The “issues” left many Blackberry owners only able to text and make calls.
Many corporate customers said they had not lost service, suggesting that the problem was with Blackberry’s BIS consumer systems, rather than its BES enterprise systems.
“Blackberry runs two infrastructures,” explained Simon Butler, a Microsoft Exchange consultant at Sembee.
“The understanding I have is that the BIS service has crashed.
“The business side runs on a different set of servers, although enterprise Blackberrys can still use messenger and the consumer services, so they are also affected,” said Mr Butler.
Such a major failure will still come as unwelcome news to Blackberry’s owner RIM, which has been losing market share to smartphone rivals – in particular Apple’s iPhone.
Many corporate clients have switched to the device after Apple made a concerted effort to improve its support for secure business email systems.
Malik Saadi, principal analyst at Informa Telecoms & Media, said RIM would have to resolve the problem quickly.
“The current situation with the Blackberry outages couldn’t come at a worse time for RIM, following some harsh criticism in recent months,” he said.
Such crashes may lead RIM and others to “re-evaluate their reliance on centralised servers and instead look to investing in more corporately controlled servers”, he added.
But he thinks customers will stick with the firm despite current frustrations.
“It will take more than just a couple of collapses to persuade loyal consumers of Blackberry services to look for alternatives,” he said.
Many of those complaining about the crash said on Twitter that they could not live without access to BBM. (BBC News)