Booming smartphone demand kept cellphone venture Sony Ericsson in the black in the first quarter, despite supply disruption following Japan's earthquake and tsunami.

Sony Ericsson posted a pretax profit of 15 million euros ($21.31 million) on sales of 1.15 billion euros. Analysts in a Reuters poll had a mean forecast for a pretax loss of 24 million euros and sales of 1.29 billion euros.

The Japan earthquake made it a challenging quarter operationally and we are experiencing some disruptions to our supply chain, Chief Executive Bert Nordberg said in a statement.

Sony Ericsson said in early April the March 11 quake, which hit component supplies for electronics firms around the globe, was limiting volumes in its new smartphone offerings and would delay the wider launch of its neo model to the third quarter.

Analysts have said this makes 2011 another tough period for the 50-50 venture of Sony and Ericsson, which only returned to profit a year ago after seven straight quarters of losses.

Sony Ericsson has slashed costs and refocused on higher margin smartphones that link to social networking sites like Facebook.

But analysts say it still takes too long for the group to bring new products to market and it has been left trailing by the likes of Apple's iPhone and PC-like smartphones from the likes of Samsung and HTC.

(Reporting by Simon Johnson and Tarmo Virki; Editing by David Cowell)