Blackberry boss on system meltdown
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.
Managing director of Blackberry maker Research In Motion, Stephen Bates, told the BBC that engineers are "working around the clock to get the system up and running."
He added that further systems will be put in place to ensure it does not happen again.