Earlier this week Nokia said its first 4G phone, which it markets with the strapline "an amazingly fast way to connect", can occasionally lose its data connection due to the bug. It promised to fix the problem around April 16.

"The update is now available. Consumers now have the opportunity to update their AT&T version Nokia Lumia 900 software," the firm said.

Lumia 900 is the third Nokia phone to run Microsoft's (MSFT.O) Windows operating system since it ditched its own Symbian system last year, and only went on sale in the United States through AT&T (T.N) on April 8.

It is due for a wider global launch this quarter. The model won several awards at the Consumer Electronics Show in Las Vegas when it was launched in January.

Nokia is offering anyone who has bought a Lumia 900 phone, or who buys one by April 21, a $100 credit to their AT&T bill. The operator sells the phone for $99.99 with a 2-year contract.

Nokia lost the top spot in the lucrative smartphone market last year to Apple (AAPL.O) and Google (GOOG.O), and analysts said it lost overall top spot in cellphone sales volume in the last quarter to Samsung Electronics (005930.KS).

This week Nokia also warned its phone business would post losses in the first two quarters of this year as it struggles to revamp its product line to compete with Apple and Samsung, sending its shares sharply lower.

(Reporting By Tarmo Virki; Editing by Daniel Magnowski)

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