* Sees phone business Q1 operating loss about 3 pct of sales
* Sees similar or larger loss in Q2
* Nokia shares tumble as much as 19 pct, while broader market up
* Lumia 900 bug can cut data connections, fix due April 16
* Customers buying phone for $100 to get $100 call credit (Adds detail on margins, sales, Elop quote, background)
By Tarmo Virki
HELSINKI, April 11 (Reuters) - Nokia 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 19 percent lower.
Earlier on Wednesday, the struggling firm said it had found a software bug in the new Lumia 900 smartphone, its big hope to take on Apple's iPhone, and was effectively giving the model away until it is fixed.
Nokia shares fell as low as 3.10 euros, their lowest level since 1997. The stock had already crashed more than 50 percent since Nokia announced in February 2011 it was dropping its own Symbian operating software and switching to the largely untried Windows Phone system developed by Microsoft.
Nokia said its phone business, which is launching a raft of new products running Windows Phone to make up for the decline of the Symbian lines, would make an operating loss of around 3 percent of sales in the first quarter, having earlier forecast around breakeven. It predicted a similar or larger loss in the second quarter, below all 29 analysts' forecasts gathered by Reuters.
On average, analysts had expected a profit margin of 0.4 percent for the first quarter, and 2.1 percent for the second.
"It's a disaster," said Thomas Langer at WestLB. "Shipments of Symbian devices are declining faster than we anticipated ... (and) the ramp up of Lumia devices is not fast enough to compensate for the shortfall."
"Nokia's challenges have been exacerbated by rampant competition - notably Apple and Samsung, who are extracting a disproportionate amount of margin from the industry at present," said Ben Wood at CCS Insight.
Nokia said competition was particularly tight in the emerging markets of India, the Middle East, Africa and China, which have been an area of strength for the company, even as it suffered in more developed markets.
Though still the world's biggest volume maker of cellphones, Nokia lost the top spot in the lucrative smartphone market last year to Apple and phones running Google's Android system, in part due to its weak performance in the United States, where its smartphones have less than 1 percent of the market.
It sold a total 12 million smartphones in the first quarter, with gross margins slipping to 16 percent from 20 percent in the previous quarter due to the fast decline in the Symbian portfolio. It still has a mountain to climb to match the 37 million iPhones that Apple shifted in the fourth quarter.
WestLB's Langer expects the problems to extend into the rest of the year.
"In Q3 we will have the iPhone 5 and (Samsung's) Galaxy S3 and so on, so EPS (Nokia's earnings per share) for 2012 is now somewhere in limbo. I think they need to start the second or maybe the third phase of a restructuring programme. It's a very difficult situation for them."
The group has already announced 30,000 job cuts since Chief Executive Stephen Elop took the helm in late 2010.
"It does take time to turn around the product portfolio and so forth, but what you see is us very aggressively going after that," Elop told analysts.
Nokia said it sold over 2 million units of all its Lumia smartphone models in the quarter to end March, up from over 1 million in the overlapping November-to-January period, but analysts said they had expected a faster uptick in sales.
Mikael Rautanen from research firm Inderes said he was expecting twice the sales volume.
"This poured a lot of cold water on investors, and I think the stock is reacting accordingly," he said.
Nokia said it would focus increasingly on Lumia phones, a task made a little harder by the data connection bug in the Lumia 900, its first 4G phone, which it markets with the strapline "an amazingly fast way to connect". Nokia said a software update to fix the problem, a "memory management issue" related to phone software, not to hardware or the Windows operating system, would be available around April 16.
It is offering anyone who has bought a Lumia 900, or who buys one by April 21, a $100 credit on their AT&T bill. The operator sells the phone for $99.99 with a two-year contract.
The Lumia 900 is currently only available in the United States, where it was launched on April 8, and is key to Nokia's comeback there.
"It's like they stalled their engine when everybody is looking at them at the start of their race," said Gartner analyst Carolina Milanesi.
It is the third Nokia phone to run the Windows system and is due for a wider global launch this quarter. The model won several awards at the Consumer Electronics Show in Las Vegas in January.
"I must say I have not encountered anything, but I have been impressed by their forthright, aggressive, and undoubtedly costly response," said Boston-based analyst John Jackson from CCS Insight, who uses the Lumia 900.
Though one analyst who asked not to be named said it would only cost Nokia at most $10 million on likely sales before the fix, it will be a big disappointment to a company struggling to revive its brand. Its share of the global smartphone market tumbled to 12 percent in the fourth quarter of last year from 30 percent a year earlier.
"To have a memory issue causing disruption to what was otherwise, apparently, a fairly good launch, with prime time ads and reasonable reviews, is the last thing they needed - particularly in the U.S.," said Tim Shepherd, analyst at Canalys, before the loss warnings.
Nokia created the smartphone industry in the late 1990s with its Communicator models and was the undisputed leader until Apple's iPhone entered the ring in 2007 and Google's Android system was released in late 2008. (Additional reporting by Terhi Kinnunen, Eero Vassinen and Veronica Ek; Writing by Will Waterman; Editing by Janet McBride)