US business software giant Oracle announced Tuesday it was buying e-commerce software company Art Technology Group for one billion dollars in cash.

Oracle is offering six dollars per share, a premium of 46 percent compared with ATG's closing price on Wall Street on Monday.

ATG shares gained 45.12 percent in New York to close at 5.95 dollars on Tuesday. Oracle shares rose 1.38 percent to finish at 29.53 dollars.

The acquisition is expected to close by early 2011, pending required stockholder and regulatory approval.

ATG provides merchandising, marketing, content personalization, automated recommendation and live-help services to businesses.

"More than 1,000 global enterprises rely on ATG's solutions to help increase the value of their online customer interactions," ATG president and chief executive Bob Burke said in a statement.

"This combination will enhance the ability to bring all their commerce activities together -- creating a more consistent and relevant experience for their customers across all interaction channels, including online, in stores, via mobile devices and with call centers."

Bob Weiler, executive vice president of Oracle Global Business Units, said "this acquisition builds upon our dedication to offer the most complete and integrated suite of best-of-breed software applications and technologies required to power the most demanding companies in the world in every industry."

Citigroup analyst Walter Pritchard said Oracle's acquisition of ATG will allow it to compete in the sector with computer giant IBM, software titan Microsoft and smaller companies, such as GSI Commerce and Digital River.

"Art Technology Group brings a robust e-commerce front-end to Oracle's vertical solutions in retail and increasingly other verticals," Pritchard said.

ATG reported its third quarter results on Tuesday. It said net profit rose to 4.2 million dollars in the quarter from 4.0 million dollars a year ago, while revenue grew 16 percent to 50.3 million dollars.

Oracle spent nearly 7.5 billion dollars last year to acquire Sun, the one-time Silicon Valley star behind the popular Java programming language.