* Q2 sales grow 9 pct vs 21 pct in Q1
* Sees H1 sales up about 15 pct, trading profit up 20 pct
* Ups 2012 fleet investment by 50 mln stg to about 415 mln stg
* Shares down 4.4 pct, top FTSE fallers
By Adveith Nair
LONDON, June 15 (Reuters) - Britain's Aggreko, the world's biggest temporary power provider, said it expects first-half sales to grow 15 percent, signalling growth slowed in the second quarter, news that disappointed investors and sent its shares down 3 percent.
The company's first-half sales forecast indicates growth of about 9 percent in the latest second quarter, down from a much higher rate of 21 percent in the first quarter.
The slowdown in the second quarter of 2012 is in stark contrast with last year, when the rate of underlying growth had accelerated to around 22 percent from about 18 percent in the first quarter.
"All regions have slowed into the second quarter (2012), especially North America," analysts at Bank of America Merrill Lynch said.
"Aggreko is a 'good news stock' and the market tends to expect an upgrade (from the company) ...Although this is no downgrade, it could weigh against the stock," the analysts added.
Shares in the company, which provides generators to cover electricity shortfalls or power live events, were down 4.4 percent to 2,065 pence by 0921 GMT, and were the top losers on Britain's blue-chip FTSE index.
Aggreko, however, said it would deliver good growth in 2012, and increased its fleet investment for the year by 50 million pounds ($77.7 million) to about 415 million pounds, citing increased order intake at its International Power Projects (IPP) business, which is likely to top 700 megawatt in the first half.
Analysts at Citi said growth at IPP should re-accelerate in the second half given 'excellent' order intake, but warned the company's Local Business unit could remain more subdued, in line with previous guidance.
Aggreko said the weakening macroeconomic environment would reduce the underlying rate of growth at its local business unit in the second half, but added this would be partly offset by the impact of the London Olympics, a contract the company values at about 50 million pounds.
The company has in the past powered other high-profile sporting events, including the soccer World Cup, the Vancouver Winter Olympics and the Asian Games in 2010.
Aggreko currently expects underlying sales to grow by about 15 percent in the first half and underlying trading profit to rise by around 20 percent.
For the same period a year ago, Aggreko had reported a trading profit of about 127 million pounds on sales of 637.2 million pounds.