FRANKFURT—Adidas AG on Thursday raised its guidance for the fourth time this year, due to gains from the early termination of a partnership with U.K. soccer club Chelsea and strong quarterly sales.

The German sportswear firm said it now expected currency-adjusted sales to grow at a percentage rate in "the high teens," up from the 15% it had earlier projected. It forecast that net profit should increase at a rate of between 35% and 39%, reaching a number between €975 million ($971.16 million) and €1 billion for the full year. The company's previous estimate was for a 25% net profit rise.

"We have every confidence that the strong momentum our brands are enjoying around the world will continue," said Chief Executive Herbert Hainer. "We are extremely pleased."

Adidas stock has been one of the winners on the Frankfurt stock exchange in the past year, more than doubling its value since last summer, although some analysts believe it has gone too high.

The company also released preliminary second-quarter results. In the three months ended June, net profit from continuing operations rose 99% to €291 million. Quarterly revenue increased 21% when adjusted for currency effects, to €4.4 billion, it said.

The company didn't break out regional sales on Thursday, but said it had grown at a double-digit percentage rate in "all key regions."

Adidas has long struggled to regain its cool image in North America, the world's biggest and most influential sports market, and the company has recently started to gain momentum in the region. Data from sports market researchers NPD Group suggests Adidas's U.S. classic and running shoe sales tripled and doubled, respectively.

According to a U.S. survey performed by UBS, Adidas's brand perception is still well below that of its main competitors Nike Inc. and Under Armour Inc. Nike is currently more than five times larger than Adidas in North America.

Mr. Hainer, who is the longest-serving CEO of a German blue-chip firm, is leaving Adidas in October.

Adidas said more details on the raised outlook and quarterly earnings would be published on August 4.

Write to Ellen Emmerentze Jervell at ellen.jervell@wsj.com

(END) Dow Jones Newswires

July 28, 2016 04:15 ET (08:15 GMT)