German sportscar maker Porsche

is bracing for slower sales growth in China this year as the country's premium auto segment loses momentum amid a slowdown in economic growth.

China's economy grew at its slowest pace in the first quarter -- 8.1 percent against 8.9 percent in the previous three months -- in three years. Chinese auto sales climbed 4.5 percent in March to 1.4 million, but slid 1.3 percent over the quarter.

Economic development in China is normalizing and the long-term outlook remains stable, sales chief Bernhard Maier told Reuters at the Beijing auto show.

Full-year growth in Porsche's Chinese sales, including the 911 sports car and the Cayenne sport-utility vehicle, may not exceed the 38 percent achieved in the first quarter, he said.

At the end of the year there should be a reasonable increase in our growth in China, he said, without giving figures.

Porsche sold 65 percent more vehicles, or a total of 24,300, in the world's biggest car market last year.

Auto sales in the U.S. rose about 13 percent in March as consumers, energized by an improving job market, replaced old vehicles and took advantage of cheap financing. The U.S. and China are Porsche's two biggest sales markets.

China has been posting stronger rates of delivery growth for several years, though the U.S. may remain the sports car maker's biggest market in 2012, due to greater demand for new generations of the iconic 911 and mid-engine Boxster roadster, Maier said.

Should the need for mobility develop as rapidly as projected, then China could surpass the United States over the middle or long term as our biggest market, he said.

Porsche, which is combining with Europe's biggest auto manufacturer Volkswagen , may tap VW resources in a drive to boost global sales to about 200,000 units by 2018.

Worldwide deliveries rose 21 percent last year to 117,000 autos, with the Cayenne SUV, Porsche's best-selling model, contributing some 60,000 units.

(Editing by David Hulmes)

Volkswagen China